Hi Mike
I think you estimate of 8-10 oz for a conversion might be pessimistic, but no matter. Even at 80 oz the power system will not be a problem.
Proved out the biggest Brodak power system on an ARF Strega that weighed in at 80 oz. Motor barely worked up a sweat and the airplane never knew what hit it. Other concerns were nose-heaviness - I thought it was OK but my brothers and nephew all thought it needed a slug of lead in the back. If the Score balanced with the Saito 62, then a heavy outrunner sounds like a smart choice. Because the 80 oz weight was right at the border for .018" lines we put it on .021" - no problem.
The heaviest part (and part with the most weight saving opportunity) of the Strega system was the battery. There are more/better motor & battery choices out there now Here's my thoughts on the Strega set-up and what I would consider today:
* APC 13x5.5 EP (an APC 13x6.5EP would have enabled the next size smaller battery)
* Arrowind 3526 650 kV (BadAss 3530-700kV is heavier but still lighter than the Saito and would help shrink the battery)
* Castle Phoenix 65A (45A would have been plenty but no important weight savings)
* 6Sx2800 at 16 oz (6S x 2200 @12 oz, but again I think there are lighter choices out there)
Not familiar with the front structure of the Score - does it have a firewall with a nose-cone style cowl? If so then it would probably be a chore to use a front mounted motor. On the other hand a nose cone would simplify motor access.
The Strega did not have any meaningful structure at the nose, so I used a rear mount on a 1/4" plywood firewall. I also removed the motor mounts. Used a top side battery hatch, but today I would make it side access to improve battery retention and stiffen the front end. I modified the ARF with a bolt on wing - I understand the Score also uses a bolt on wing? Just the thing for a dad with two sons who fly stunt and a single SUV to get all of them to the contest!
So besides the fact that a 80 oz stunter is a load to hang on to, yes, I think you can get there from here.