Oh and forgot you definitely want to use a real garage door company who specializes in garage doors only especially for a job like that. Those goons at the box stores would have it screwed up pronto :lol_hitti
If wanting a jack shaft opener to do it properly you should have at least a little bit of high lift or you will throw your cables off of the drums when operating the operator. Ive seen it done by "cheating" and using bumpers on the end of the horizonals and letting the door hang slightly below...