I did a similar conversion of an Airtronics Olympic 650. I was sloping it a lot and wanted more durability. The entire fuselage was glassed with epoxy. [X(] The result was a winged baseball bat!
Calculation showed the stock horizontal tail to be oversize. The horizontal surface was almost all fixed stabilizer and very little elevator. At first I simply removed the vertical fin and rudder, cut the stabilizer and elevator in half, and reattached the stab at an included angle of about 110 degrees. This removed the weight of the vertical surfaces without adding anything, so the nose got quite a bit lighter. The result was a glider that was very stable but not very responsive.
New surfaces were built using the same external shape but with the hinge line moved forward. Now the elevators were more like 35 percent of the total area. This resulted in an easy-to-fly, stable, and responsive glider that would self-thermal with a bit of elevator held. It was a real pleasure to fly and fuselage breakage was impossible!