Hi Mattressmatt,
There really isn’t any rule of thumb when it comes to mattress thickness. Some people may do very well on a 6" latex mattress (or even thinner) while for others an 8" innerspring with say 5" of latex on top of it with some progressive firmness may be ideal. It really depends on the specifics of the layers and components of the mattress and how they interact with each person. A 6" innerspring with only two inches of polyfoam above it on the other hand may be too firm. I wouldn’t use mattress thickness as any kind of a guideline except I would tend to avoid comfort layers that were too thick and soft regardless of the type of support layer underneath it. On the other hand … differences of an inch in comfort layers can make a significant difference in the “feel” of a mattress. I would avoid trying to choose a mattress based on specs unless you had extensive experience with how different combinations interact or specific reference points based on your own testing that were very close to what you are considering.
Latex is the most breathable foam category (Talalay even more than Dunlop) so it helps with temperature regulation more than other foams but the foam in a mattress is only one part of all the factors that combine to regulate temperature which in some cases can have an even bigger effect on a mattress. There is more about the combination of factors that are involved in temperature regulation in post #2 here.
The “feel” of a mattress is very subjective and most people have had the experience of testing mattresses earlier in the day and then going back to retest the same mattress later on and it felt completely different because the testing in between has changed their frame of reference. While “feel” is certainly part of any mattress choice and some familiarity with the different characteristics of different materials and components is important … it’s more of a preference issue and pressure relief and alignment are more important yet. No matter how good a mattress feels in a showroom … if you wake up with a back ache or pressure points then it would not be a good choice. Feel also says nothing about the quality or durability of the materials in a mattress. 10 minutes of “feel based testing” isn’t enough to predict how well a mattress will work when you sleep on it and could have even lower odds of making a successful choice than random chance alone (see this study). in other words it’s just one of the factors in a good mattress choice and is based mostly on preference and not on “needs”. One of the links in the read first post (post #4 here) goes into all the different factors that are involved in an “ideal” mattress choice including “feel”.
They are a husband and wife team and are probably not technology savvy. Some of the better “finds” I know of around the country don’t even have a website at all but are dependent on their local reputation in the area for business. Their phone is still working and they answer with “Tucker mattress Company” so I suspect that there is an issue with their website or domain and they are still in business. Since the introduction of 1633 which is the new fire code that came into existence in 2007 I’ve seen about 20% of the local manufacturers across the country go out of business as the “advertising dominated” major brands and chain stores increase their market share and it becomes more difficult to compete against consumer perception based on the massive advertising of lower quality more expensive mattress that have good “marketing stories” attached but I think they are still there making mattresses. You can see a few comments about them in post #2 here. They are certainly worth talking to.
That would probably depend on their policy about building a custom mattress on “spec” or on how confident you were after a conversation with them about a mattress that was based on “tweaking” one of their standard designs. I would personally stick with a mattress you had tested or a small variation in design that had a more “predictable” outcome unless you had good options to change out a layer or make fine tuning adjustments after your purchase. This would be part of the conversations I had with them because I don’t know their specific policies. Many manufacturers will make changes to a mattress after a purchase which of course makes more custom designs less risky. I haven’t talked with them so I don’t know much about them other than the basic types of mattresses they make.
They are really informative and knowledgeable on the phone and I would encourage you to talk with them to find out more about the differences in their different mattress lines because they will give you more specific information than anything I could say. In general though their top two lines are more “boutique” brands that are mostly sold through various retailers around the country which use more costly cover fabrics and materials. They really don’t have much competition at all in the major brands although they are their higher priced lines. They don’t “compete” with their retailers (which is the quickest way to lose your retailer base) so their direct prices aren’t lower than they are generally sold at stores. Their Invigo line has lower margins and uses blended Dunlop with Puralux Dunlop in the comfort layers and are more “value” priced. You can test their mattresses in person if you make an appointment first.
As long as you focus on materials and on your own personal testing more than specs you will be fine and you will normally find these types of local manufactures to be open, easy, and informative to talk with. They really do like to talk about the mattresses they make 
Phoenix