Can any o e tell me the structural difference between a 1030 and an 1100 ?
I have inherited a 1030 kit and built it as light as possible and would now like to fit a 447 or 503 , in England the wieght is not a problem as our "" SSDR" class has 300 kg . Can any one comment on my plan please . RiP

This is a sound plan.  The main difference between the two is the 1030 is built with a lighter tail.  Not weaker, better engineered. I believe there is also some very minor weight saving in the drag truss of the wing. The 1030 was designed to use the lighter single cylinder engines but I have seen one using a Kawasaki 440.  The 447 or 503 should work fine.

1100 model uses the heavy tail and brace tubes. The seat back is now at station #4,and is no longer a full width seatback, which allows for more leg room and short pull pins for the rear spar attach point . Wing has a lighter(smaller) bottom spar cap. RS-8 instead of  RS-9. Fuselage is 2" narrower. Might be a few more differences that I have forgotten, but basically, the 1030 is the old original miniMAX airframe with streamline cowel, cockpit area and rear decking.
  The original airframe had a lot of 447s mounted to it and some 503s.
I would have no worries about the airframe as long as it was built per plans.
Larry

I realize this is an older thread, but I want to thank everyone for the information and answers to my unasked questions. This confirms my decision to opt for the MiniMax 1103R over the 1030F. BTW, the 1103R is the 1100R but with the lightweight tail.