I'm glad you picked up Skitarii ! As long as it's what you really want it's all that matters
As for the magnetising I never tried it myself but it's most certainly a good idea, and I heard it was easy to do on Onagers. The thing is to magnetize the part of the gun that meets the chassis of the Onager so as to easily replace it with another weapon should you need it if you switch weapons in your list. I'll have to let someone else answer for that magnetising part.