I also have the same sig pro softy. I wanted a flush / drop in setup so we pulled out the carpet and pad.
You basically need to build up 2 & 1/2" to 2 & 5/8" for it to be flush with the SPS.
So starting from the wood subfloor we have 1" pink foamular insulation board as the first layer which is sold in 4 ft x 8 ft pieces. Next layer is the 1" EVA foam jigsaw mats. And finally the turf is Money Putt by GrassTex which is great.
So we built those layers up and then cut in the space for the Sigg pro softy and dropped it in. The foam boards were used to provide a solid but easy to cut base layer but you could do a 2 inch foam base as well and I think it would work out just as good.
If you happen to be in the North Texas area and decide to proceed, I actually have an entire box of the EVA foam tiles that were just surplus.
I bought the turf from Golf Sim Depot as they were offering the best price delivered. The foam tiles just came from Amazon and the pink board from Home Depot.




