I'd bet you could get the Nitro 1.5 cams on an Onza. That would put the draw length down in your range. Martin's catalog doesn't show the 1.5's for anything other than the Crossfire and Shadowcat, but I don't see why they couldn't be used on any other Nitro cammed bow. I'd talk to a dealer about it, or give Martin customer service a call and see what they have to say. I've thought about looking into an Onza with the 1.5 cams myself. That would put the max draw length at 28.5, which is what I shoot.
2006 Rytera Bullet X 60#---2008 Moab 70#
2008/12 Firecat 60#--- 2010 Warthog 70#
2010/2012 Alien X 65# 2011 Onzas 60 & 70#
2009 Warthog 70#---2009 Firehawk 70#
2010 Strother SR-71 65# & 2012 Strother Rush 65#
I hunt, therefore I eat. lol