The Mamba 90 is already fitted with the 1.5mm trigger pin, and has a very sensitive trigger pull. However, if you have the spearline rigged tight, the line release puts a side load on the trigger, and makes it very stiff.(this can also cause the gun to go off when the safety is taken off, solution, never use the safety! ) This is a problem on all air guns. Either rig the line more loosely (may be a problem with braid as it tends to stretch when wet, so use mono) or put a bit of bungee around the barrel and tuck the line under that instead of using the line release
As regards aiming, I think any speargun should be pointed with both eyes open, rather than aimed. I cant explain how I align the gun, it just happens, the same as when using a shotgun
The smaller standard Mambas are a bit nose heavy (the 110 balances beautifully as it was the "original" Mamba) but I think this is a price worth paying for the greater manouverability of the 30mm barrel. The Magnum version with 40mm barrel floats slightly with a 6.5mm spear but balances nicely with a 7mm
cheers
dave
www.spearo.co.uk
www.eliossub.co.uk