.35 Barrel question

[YEMX]

So I've been kicking around building another .35 Rifle.  I'll be using a Texan as the base rifle this time around.  I'm looking for some input on twist rates and such.  I think I know the answer, but I want to chat with y'all before I decide on anything.  The experiment (barrel) would be pricey, hence me asking for advice prior to any money being spent.

The base rifle will be a Texan LSS, so barrel length will be anywhere between 28"-34".

Known twist rates:

TJ: 1:26 (not sure on O.D. It's been a while)
Airforce: 1:26 (16mm O.D.)
FX: 1:25 (at least per Utah AG's website.  If there's a Superior Heavy liner with a different twist rate, please let me know) (O.D. moot, I'm not adapting a FX barrel to a AF rifle)

What are the thoughts on a faster twist rate?  Like 1:20?  There's faster, but 1:20 is the one I'm looking at, since it's close to 1:26.  I'm not saying NO to faster twist rates than 1:20 though.  Hence the post.  Any/all input is welcome. 

I know twist rate depends on weight and length of the projectile and right now, I'm just looking at commercially available slugs.  I won't say no to cast of course, I just don't physically have any molds to start off with.  But lets say I'll keep the slug weight to between 100-150 grains.  Not sure of the lengths- just take a look at all the slugs at Pyramid Air, since that's where I'm starting for slugs.  I'll of course try heavier, and I don't think too light (like 68 gr) would be appropriate, given the platform.

So what are y'all's thoughts?  Just stick w/the 1:26, or would 1:20 be different enough to try?  Not worth the hassle and expense?  Really, the only "benefit" would be a thicker (therefore stiffer) barrel, and a overall heavier rifle (this is for prone or bench shooting, not lugging around).  TIA!!