Hi Kerry360,
As you know I think you certainly made a great quality/value choice … and congratulations on your new mattress 
I’m looking forward to your comments and feedback once you’ve received it and have had the chance to sleep on it.
[quote] Does anyone have any experience and/or advice regarding this one:
www.amazon.com/Zinus-Platform-Mattress-F...01DLB7MPU?th=1&psc=1
The Zinus Modern Studio Platform 3000 claims to be made of stronger metal than previous versions and the manufacturer said the slats are 3in apart on one of their other models (not positive about this one).[/quote]
An all latex mattress will generally do best with a firm, flat, and evenly supportive support surface underneath it that has minimal to no flex under the mattress and for larger sizes with at least one center support beam that has good support to the floor to prevent any sagging in the middle of the mattress. The components need to be strong and durable and stable enough to support the weight of the mattress and the people sleeping on it without some of the parts bending, sagging, or breaking over time. The support surface under the mattress should have enough surface area to prevent the mattress from sagging through any gaps or spaces in the support surface over time but still allow some airflow under the mattress. I would suggest that in a slatted support system (either a foundation on a steel or wooden bedframe or a platform bed with a slatted support surface) that any gaps between the slats are no more than 3" (with 1 x 3 slats) although less than that would be better yet.
There is also more information about the different support systems (bedframes and foundations or platform beds) that are generally suitable for different types of mattresses and some examples of each of them in post #1 here.
While I don’t have any personal experience with it … I would tend to avoid the Zinus platform bedframe you listed (and other similar platform bedframes as well). The steel part of the bedframe does look a little stronger and more stable but the wooden slats may be somewhat thin and flexible rather than rigid (I would look for 1 x 3’s for the slats) and based on the number of slats it also looks like there is more than a 3" gap between the slats as well. It certainly wouldn’t be my first choice.
Phoenix