: I used the foam shavings that were left from shaping my seat, along with an
: assortment of sawdust, microballons etc. I don't know how strong it is,
: but so far it has not blown up on me, and seems to be relatively light.

: JJ
I like to bond a SS U-bolt in the end pour so I like the consistency of the micro ballons. The wood blocks would also work with the u-bolts.
Don