Personally, I don’t think [name]Max[/name] works, but feel free to do it anyway 
I do love [name]Magnus[/name] and think it doesn’t need a nickname, but if you want one you can try:
[name]Mag[/name]
[name]Mags[/name]
Magnie
Mansie (:P)
[name]Manny[/name]
Magna