DIY mattress build

I'm 5'4" 250 LB male currently sleeping on a very firm bonnel innerspring mattress with a 3" SOL topper. This combination is still too fire and I suffer from sore hips and a back ache every morning. I'm considering using the SOL topper as a starting point for a DIY build. I'm considering a base of 4" HD 36 high quality foam from the foam factory as a base layer, the 3" SOL medium topper as a transition layer, and a 2" SOL soft topper as the comfort layer, with a SOL zippered cover. Would this be a reasonable build considering my height and weight?