I have used all types of guns over the last 30+ years, fom timber to tube.
Still not any sort of expert but I have settled with a KES-Peter Kesby gun from Australia for most to all of my spearing. Using a cut down tube to shoot inside the caves for what we call pigs.
The KES is one of the best hand made guns I have used with a perfect balance and matched rubbers which dont need a body builder to load but still shoot straight at full stretch
As far as mid or rear handles go we used to use the mid handle so we were able to control the kick back with our other hand. I prefer the rear but if the gun is balanced its your preference what works for you.