10 3/4 lbs. YS 120 FZ for power. No need to strengthen the firewall over what is in the instructions for a Magnum 120. I only put some tiangular support on mine.

Mine is too heavy, really should aim for under 10 lbs to get a really good flyer.

If you do a search on this site there are plenty of threads on the Ultimate, it is a popular plane.