Hi TedLogan,
Yes … this is the same concern for everyone when they buy a mattress, a topper, or a combination of the two. The balance between the two main functions of a mattress which is the opposing needs of good comfort/pressure relief (which requires softer materials) and good support/alignment (which requires firmer materials) is the most important part of choosing any sleeping system or component and is part of the “art and science” of all mattress theory and design that makes one mattress or combination suitable for some people and not for others. Too much or too little of one (either comfort/pressure relief or support/alignment) can lead to choosing a mattress or “sleeping system” that produces symptoms in the other and either doesn’t provide good alignment in all your sleeping positions or doesn’t relieve pressure points.
Careful and objective testing on a mattress or a specific mattress/topper combination can do a good job of predicting how a mattress or mattress/topper combination will work for you in real life in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) but if you can’t test a specific mattress/topper combination in person then the topper guidelines I linked (which are based on your experience and perceptions on your mattress), a more detailed conversation with a knowledgeable and experienced manufacturer or retailer who is knowledgeable about how the toppers they carry may work for different people on different mattresses, and/or a good return or exchange policy if you aren’t confident in your choice has the best chance of success and the lowest risk.
The better options or possibilities I’m aware of in the Indianapolis area are listed in post #2 here. I don’t know which of them carry toppers or what their return policies are but a few quick calls will easily find out.
Phoenix