RE: Seagull edge 540 .46 size CG?
I used the 9.5 cm and had no problem ... if anything it is level at 9.5 so I made it slightly nose heavy with .5 oz of weight on the firwall ... Check your mesurement on your motor mount ... I actually moved the motor back to 112mm and just put the cowl back 3mm more . Just try moving the motor and find a way to temp secure it .. I know I am lighter than you as I am running an Irvine .53 12 X 6 prop , Alum. Spinner , but also using a longer pipe than standard ...
I will add advice is to change the landing gear to a 1 piece or take a thin strip of alum. or Carbon fiber and bolt the two together.
I had a dead stick ( Ran out of fuel ...DUH) and just bounced lightly (Panic set in ) ... well the two peice gear gave on the wood it split right down the middle .... So I found the weak link in the plane . LOL
If you want any other suggestions send a note and I can Pass them on to you . I found a list of things I would correct in the original build..