For the information of all.....Hysol, and for that matter any epoxy
adhesive, doesn't actually bond onto plexiglass. For sure it sort of stays
attached but in reality it's not much more than a surface tension bond.  Try
some test pieces....Hysol some plexiglass scrap pieces to a composite
surface, when cured lift a corner with a sharp chisel and the the two parts
will just split away from each other...the bond is only a little better than
an epoxy part on release tape. In fact the release tape has a stronger
adhesive than the bond of hysol to plexiglass.

There is a two part polyurethane adhesive made by Casco of Denmark which is
suitable for bonding plexiglass to composites. I understand there are other
similar products by other manufacturers which may also be suitable, but best
you do your homework if you want to use them. Casco about a year ago made
their last batch of their adhesive, but I've heard a rumour that they have
continued production but I can't verify this. I know for certain that
Lancair Kits has known about the lack of bond of epoxy Hysol to plexiglass
for a year or more....perhaps there's been a 'head in sand' attitude hoping
that the problem is not a problem.

Ciao,

Roberto d'Italia.