the kevlar tanks are not that great if you ask me , they have a very terrible seam for the top tank that the clunk has a hard time to deal with
as far as mounting the turbine , i would mount it as far forward as you possible can , to avoid adding extra weight ( be it lead or larger batteries )
keep it as light as you possible can.
try mount everything as far forward too
the merlin 100 is a light turbine , so that really helps with the weight issue