Hi!
Your Magnum .40 XL not having enough pulling power in a trainer....?? Strange? Put on a 11x5 or 11x6 APC and see if that works better. OS .46 is way too much power.
Most ball bearing .40 engines are usually just too much power for any high winged trainer airplane. Choosing the right prop and propsize is what makes airplanes perform.
Been training people fly for over 30 years!

Regards!
Jan K
Sweden