Hi Peter,
you should be able to easily find space with thin OAG's such as
http://www.teleskop-express.de/shop/...ial-Offer.html I would have thought? I was turning my mind to this today as to whether I should use my MPCC or RCCI for my new CCD. You could add a 10mm spacer then perhaps a 17-23 variable spacer on the MPCC side of the OAG eg
http://www.teleskop-express.de/shop/...-17-23-mm.html
Camera 13mm - t2 adaptor 2mm - tsoag9 9mm - m48 10mm spacer - 17-23mm spacer @21mm - MPCC = ~55mm
Russ
edit: I always get confused trying to calculate these things, email TS they are helpful finding solutions.