Brakes brakes baby

Sooooooo, I’m building a Soma Buena Vista for my wife.
Soma says you can run 650B wheels with extra lng reach brakes.
Bought a set of Tektro R559s - no dice. About 2-3mm short.

Any suggestions? Anyone had experience with these frames?

File 'em?

Dia compe 750 centrepulls.

2mm more reach than r559.

Or bdop drop pad holders.
http://www.bdopcycling.com/BDop%20Offset%20Holders.asp

Or gigantex holders
http://www.bikehubstore.com/product-p/gtxholder.htm

So do Dia Compe 750s work ok?

Bdop holders look ok.

Or just go 700C wheels, smaller tyres & a Soma front rack I guess.

Anyone got any of those pad holders locally that they wanna offload? or know of anywhere to buy locally?