Shortened the 101 3.2x8mm rivets down to 3.2x5.2 and installed on trailing edge. Approach to shortening was to use a scotch-brite wheel on the bench grinder with a template made of three popsicle sticks that would take the rivet down to the first mark consistently. This seems to work better than holding with pliers that scuffs up the edges of the rivet head. Others use a rotary cutting tool I believe, but this method seems to work for me with limited squashing of the material - just my preference.
In my wing kit there were 200+ "RIV-141 3.2x6mm" rivets included that are never referenced in the instructions. From some online resources there is a suggestion to use these 3.2x6mm rivets on the trailing edge skin support, but I thought I would confirm with the factory before using. The response from technical support I received was -
"We have recently stopped using the 3.2 x 6mm rivets because we had issues with the rivet not pulling properly and remained loose. This was time consuming to drill out and replace again. We prefer to use the modified 3.2 x 8mm rivet. You are welcome to use the 3.2 x 6mm rivets.
Both rivet sizes needs to be filed a bit at the bottom after pulling them to make sure they clear the flap.
It should not protrude more than 2mm – 2.5mm below."