Setting a Americast Tub
 

Hi.. I installed a new americast tub yesterday and notice it creeks
when I stand in it. The sound seems to be coming from along where the
tub sits on the (full-length) stringer. I've read where people have
put cement (in garage bags) under their tubs to make them more solid.
Would it be OK to do this with the americast?

Also, the directions call for putting roofing nails just above the
tub's lip (into each stud) which I haven't done yet because I noticed
this creeking problem. Once I bang these nails in, do you think the
creeking will go away?

Thanks alot. Ryan.

Exactly what is this tub made of?