It looks quite good so far, I think that I should give it a try as well

A few things I found out in the last weeks are, that TargetMap is 32bit rgba with 8bit per channel (I wasn´t able to change that-.-).
You can change a bmaps format through bmap_to_format which gives you a few more possibilities for the format.
So, if you need a high precision, you will have to render to a bmap and use that one instead of TargetMap.