Convert a universal head rivet-based kit to flush

[pylon500]

As a retired aircraft sheet metal worker, the first choice would be to see how much you could do in solid rivets, as they will expand to fill the hole as they are drawn.
Part of the deal behind 'dimpled' countersunk rivets, is that the skin shear loads are partially taken by the interlocking dimples, which could go some way to compensating for a lesser shear value rivet.
To that end 100° will interlock better than 120°.
If you have to go blind rivet, have you looked into metric (Russian/Chinese) rivets?
1/8th rivet is around 3.3mm, they may have 4.0mm?
On low/mid range speed aircraft with non laminar sections, you would only need bother doing the leading edges back to the spar, you would need to determine if the spar is far enough back to be out of laminar flow, and not gain an advantage by being countersunk along the spar.
It's interesting that Cessna often countersink along the spar, but their spar is a long way forward on a non laminar section.
Piper claim to use laminar sections, with the spar a long way back, but I don't think they countersink/dimple the sparline, (maybe on the Comanche series?)
I don't know what prices are like in the US, but here in Australia, if I riveted an aeroplane together with Cherrymax rivets, they would be HALF the total cost of the aircraft!!
CR3242 4-2 can be about $1.50 each....

[Bob H]

If your skins are .016" thick and you are making a single lap shear coupon for testing between various rivets, the skin will fail in bearing long before the rivet will shear, around 160 lbs for a 1/8 dia sold rivet.
So installing Cherry Max is a waste. A solid 1/8" rivet will fail around 360 lbs, 2X stronger than the skin will accept. I'd stay with the factory callout.