Well the main on Lola is far from stiff. Its the main that came with it new. I think my idea will work ok.
I think your idea is fine. Just get the proportions right (google "lazy jack system" in Google: here's one: http://www.cncphotoalbum.com/doityou.../lazyjack1.htm
and you'll be fine. Just remember to tap the boom carefully for the eyestraps and use Tufgel or something similar on the bolts, ditto for the cheekblocks.