I'm thinking of doing one…

Kona A, had a pivot concentric with the bottom bracket therefore no chain growth. If there's any left, it was a few years back…

Kona ?Cowan? does the concentric pivot too

You could go for a frame that pivots around the BB like a Kona Bass or A Cove somethingorother. With these theres no chain growth(?) so tensioning the chain isnt a problem

I've seen it done on an orange patriot too, theres a topic on SDH about it. Think he used a rear mech and part of a chain guide to tension the chain.

Cant be arsed writing anymore now but if theres more questions, fire away

just needs a bouncy fork

Had a couple of Cowan DS frames (predecessor to the Bass) and a Kona A. Shock with lock-out is a godsend (used RP3 and RP23 on the Cowan and Vanilla RL on the A).

I've got a mate who runs a Kona A with a manitou SPV air shock which seems to work for him. It goes up hills faster than my inbred anyway….

Why?

Lenz Milk Money

ignore the "why's" i loved my "A"

i miss it, i love the 05 version of the A frame shame no one imported it.
your best option is the Cowan frame above.

If the why is directed at me…

Its because I want another bike.

What about tensioners? Yess??

I always fancied ssing a trek y bike – one if the carbon ones. Or a Klein Mantra

Surely if you run a tensioner chain growth isn't an issue (as long as it's adjusted right), so you could use any frame. Probably a tensioner with two wheels (like a non-shifting derailleur) would be better.

On the A and Cowan there is no chain growth as it rotates around the BB..

no need for a tensioner.

Nor on the trek or Kleins I mentioned which are urts