Ed,
I like it; well both of them.
I'm going to get GT's 5" model and go with that; couldn't decide if 4 or 6 was better!
An 8" bull/slab is likely to be too heavy for the standard mainspring,would likely to go lighter.
Ed, your 6" bull bbl is approx 2 oz. heavier than an artillery 8" bbl., and close to what a 12" carbine bbl would weigh by my estimate; and about the max weight that would work reliably without monkeying with the spring.
The Art. mainsprings I've measured by my method are 14-16 lbs, and the 4" measures 18-20 lbs.; i.e. he heavier bbl requires a lighter mainspring as observed. It is impossible to predict what is in any given pistol, due to the natural variation and years of potential changes. The higher velocity from the longer barrel helps some also.
I also proved this to my satisfaction in working on a 12" .30 cal bbl, and getting it to a weight that would function.
Bottom line- if it works - super!!!
The 6" pistol looks great with those grips too.
Just a teaser, at Rich's instigation/idea, GT and I are going to work on an adjustable rear sight to be added to the rear toggle- wish us luck!