Bob,
The original users of the old fishtail matchlocks had the same amount of arms , legs and heads as we do, so yes, just like any other stock, they can be made Extremely comfortable to use.
Also like any other stock, if it's a generic type it may not fit.
If you make one, cut out a board shape first and try it to your shoulder. or, take the measurements off a nicely fitting gun you own.
Comb height needs measuring where your face fits against it, and what it does further back and forward matters little.
Same with LOP. Go by middle of the butt for that measurement.
If you lived closer Bob, you could try mine and see how it would work for you.
Sorry I didn't have a decent picture of overall, Bob.