A friend has gone a bought a Kona Stab for silly cheap.

However, it's got 9spd (yes I know it's a gravity bike) and he wants to put a double on it so it's actually rideable and he doesn't have to get off and push everywhere.

Had a look at the thing last night and gave myself a hernia trying to lift it, but on the seat stay it's got a cable stop and looking at it an X-type front mech would fit. it's got a 38 and Bash on there so I was thinking stick a 32 and 38 to replace the bash with an 11-34 cassette and that should make the bike more "rideable".

What do you think?

I think he'll be hard pushed getting that up a hill with anything other than a proper granny-ring. 22/36 is a common double ring set-up, it's never gonna be slick shifting but it'll work fine in a 'one for going up and one for coming down' kinda way. 

I've never been a fan of 34t cassettes. I found the 34t ring rubbed off the top jockey wheel permanently and drove me nuts, maybe I just had the B-tension set wrong.