Any of you out there flying a Max103 with the Hirth F33?  If so, how close is the weight and how is the performance with this combo?

Anyone running a Polini 250?  Sounds like that might be a nice option as well (though a bit of a hit on weight).

http://www.beliteaircraft.com/polini-thor-250-engine-review-the-best-ultralight-engine-weve-seen/

The airplane was designed for a Rotax 277 that is about 20lbs heavier than the F33.
The F33 is light, maybe too light, need to be careful that you don't end up tail heavy.
Don't add anything behind the CG like a BRS or strobe.

At idle, the F33 vibrates horribly, smooths out from about 3000 RPM and up.
Watch the EIS to get a sense for the vibration:
https://youtu.be/vdeP8E3ZZQ8

Not flown it yet so can't really comment on performance.

Depends on which Hirth F33 you have, with electric start and pull, with battery between rudder pedals. WB turned out ok.

Jumps off ground in short distance.

I would "anticipate" that a lighter fabric system (like Oratex) might help in the CG department somewhat as well.

David Cooper would know. I'm sure he is right.

Tom