Hi Phil
I setup hundreds of the Older Magnums, 40s and 44, these are GPs These were made by Thunder Tiger, and not Chinese made.. before that company was formed, they make great stunt engines, and have a nice 4/2 run, or you can use higher RPMs if wanted, they are pretty powerful and will turn a 12 x 5 props, I used them on Chipmunk , Acko sized stunters, and had other using them on full size Vectors. use 23% oil half castor, and whatever nitro that is needed, normally 5% winter 10% summer.
Randy