Sparky, when I was testing macro lenses I had the good luck to have access to the late Charlie Barringer's collection. So I tried multiple examples of some, not all, of them. They weren't all equally good. Surprising bad results generated a retest to check for operator error. Many are the ways to screw things up.
You're a little unjust to Kerry and Chris. They did a small pile of 90 Angulons, got interesting results. They're not all equally good and even late ones can be awful. Still and all, without resources one uses or tests what one has and hopes for the best.
With used lenses, condition is always a crapshoot.
When I was testing I was motivated by curiosity and by a goal, of shooting 2x3 macro with my 2x3 Graphics. So I really needed short lenses because of problems getting the extension. I eventually solved the extension problem by making a tandem Graphic -- two 2x3 Graphics front-to-back with a coupler between them. The longest focal length usable with it is around 480 mm. Anyway, when I decided which macro lenses to keep and got on with project they were for -- shoot fine details of small dead fish at home instead of trekking into the local natural history museum to use a Wild Photomakroscope -- I found that 5:1 was more than enough. Too soon old, too late smart. And I tried my 55 MicroNikkor only after I had 25, 45, and 63 Luminars and a 100/6.3 Neupolar. If I'd tried the MicroNikkor first I'd have seen it as good enough and would have stopped trying things out. As I said, too late smart.
I'm not surprised you shoot with flash. Motion is such a killer. Another reason I didn't want to use a Photomakroscope. The ones I've used have incident lighting and my subjects really needed transillumination. The one I used at USNM was on a slightly tilted bench. The subject had to be weighted down and even then some shots had motion blur. Flash, with GN calculations, is so much more effective.