[spaghetti]

The correct spear lenght for a 75cm euro gun is 115cm.

For wood on the sides, there is no rule. It depends for example on how thick the wood, or on the sort of balance you want for your speargun (more stable, more manouevarable...).

In any case I wouldn't use a 7mm spear on a 75. Heavy spear+short band stretch=no velocity. I'd stick with a 6,5mm spear, but this is me.