TargetTalk

Purely because of availability in aus i bought a locally made shooting mat. It is made for fullbore/ palma shooting and as such it doesnt have much padding as its designed to be used on grass.

Given there is a max thickness for mats does this mean more is better. I will put some more padding in but im not sure how much to add

As much as needed to make it comfortable but not so much as to be like a spring.

The Kurt Thune mat is probably the best I've ever tried, and it has at most 2.5cm of foam padding for your elbows. That foam, though, is good, dense, high-quality stuff, not cheap fluff. The thing I'm getting at here is that density is more important than thickness when it comes to padding. Find some decent, closed-cell stuff and see how much you like.

How dense would you rate it compared to a yoga/exercise mat

Less dense than most yoga mats I've seen, but equally resistant to compression.