Hi!
The Magnum .52 is a fine engine no doubt about it!
Some questions.

Here is what I would if I were you.
Fuel: I would run 20% castor oil and 5% nitro and the rest methanol...I mix my own fuel like many do over here in Sweden.

Tank: When I use ordinary R/C tanks I use the Uni-flow principle with 2 clunk tanks. Not necessary... but a little better than a one clunk set up. Tettra "bubbleless" isthe best tank...but of course not necessary!

Engine and tank : Magnum .52 is a very good engine but like all engines it has to be mounted right to function well. Always follow the old rule that say: -Mount the tank so that a the carb intake orifice is in-line with the center of the tank when the airplane sits horizontal. This is very, very important!!!

Engine: Mounting the fuel valve to carb helps in having a good engine set up. Check head shims. If it has two shims and you run just 0-5% nitro ...remove one of the head shims.

Glow plug: OS 8, Enya 3 or 4 or Nova -Rossi or Rossi 3 or 4.

Prop: There are many that work...like 9x8, 11x6, 11x7 11,5x6 APC , 12x4, 12x5, 13x4 and so on. Some good props are APC ,Bolly, Graupner "Cam-prop" and RAM. See too that you balance them.