Hi LisaD,
Some of the links in mattress firmness/comfort levels in post #2 here may give you some theoretical guidance but these are only generic and not specific to each person but they may be helpful.
Your own personal experience and testing is really the only reliable way to know whether a mattress keeps you in good alignment and I would go by any actual symptoms you experience on the mattress (such as back pain or discomfort in parts of your back) in addition to just eyeballing your alignment because each person’s physiology may be different and it can be difficult to follow the exact line of your spine or know if it is in neutral alignment (for you) in some sleeping positions.
Other than what it may look like … what specific symptoms are you experiencing? Do you have pressure points or other symptoms or discomfort when you sleep on the Pamper by itself without a topper? What is the density of the memory foam in your topper (lower density memory foam may be too soft to provide reasonable support under the lumbar curve)?
There are also some ideas and suggestions in post #11 here and post #4 here that may be helpful about ways to create a form of direct zoning under specific areas of the body that may need more support for those that have a bigger differential between their waist and hips (usually women) or their waist and shoulders (usually men).
In most cases … no matter what the price or value of a mattress … it’s a good idea to make sure that the mattress is suitable and has been carefully tested for PPP before you buy it (or has good options for exchanging the mattress or individual layers) because even the best quality and value mattress has little value to someone that can’t sleep on it. Supportive in terms of firmness is not nearly as important as how evenly it supports your body profile in neutral alignment (for you) in all your sleeping positions.
It would be helpful to know the specific physical symptoms you are experiencing and the part of your body you feel them that need “correcting” rather than just what your alignment looks like on both the mattress by itself and with the topper. This would be more helpful to make educated guesses at the reasons behind them and some solutions that may be worth trying.
Phoenix