I think you may want to ask this in the IMAC forum. The zdz 40 and MVVS 160 are the only gassers I've seen on a pattern plane. If your stuck on a DA 50, the Imac guys have more experience.

My opinions:
I dont think a 3D plane can fly pattern very good. Sure there are planes that claim to do both but dont do both very well. If I were going to do the IMAC your doing I'd get a inexpensive pattern plane. It would be easier to fly than anything scale. Sounds like your minds made up so go for the DA 50 and have a blast. Maybe at least try to fly someones 2 Meter pattership to see what I'm talking about. I think most would agree if they couldnt have a 40% er they would have a 2 Meter patternship for Basic IMAC.