airgunsmith/tuners in south island ?

Thanks for the link EC, if i get a tbt kit, I'll keep the prosport for sure.

Mine for hw dropped strait in.
The spring sizes are different between full power and 12fpe.
The spring for hw was a bit shorter due to the addition of bottom guide and slip washers. It is noted on the sight that if you get the wrong size spring or try putting the original spring back in, it will be too long and the sear won't catch.
But thats only from my one experience and im totally stoked with the resaults.

Ive already been in contact with Nic regarding this.  While the Diana 31/34 kit should be a drop in, I'm going to take the gun apart, take some measurements and send them to him.  I'm pretty sure there is a video on his YouTube channel that covers off what measurements he needs for this.

You get the "Twang" because the spring is too lose on the steel guide tube. It needs to be a nice tight fit around it. When the spring compresses it unwinds and gets slightly bigger. When you pull the trigger and the spring un-compresses you get the twang. to fix this without buying an expensive kit you can get a plastic coke bottle. cut it out to make a sheet. Then wrap that around the guide tube. This will last a while till you find a more permanent solution. and it does work as i did that on my TX back in the day before i machined up my own kit.