Hi godeep,
Nice gun you have. I was looking into getting one a few months ago.
What size and type of fish are you going for? I recommend taking a look at the spring steel South African shafts in 7.5mm from
Rob Allen or
Mako.
They are a lot stiffer than the Riffe shafts in 7.1mm and would work well with your Riffe Euro using either two 16mm bands, or two 17.5mm bands, or three 14mm bands.
If you still want to try the 8mm shafts i would recommend the South African spring steel shafts for euro mechanism from KJ that Florida Freedivers sell (its not on their site but they do carry 8mm euro mechanism shafts). These will be a lot stiffer than the Riffe 8mm shafts as well.
Spring shafts do rust if you don't take care of them, but they are a lot studier. Plus you can get 2 spring steel shafts of different diameter for the price of one Riffe shaft. This would give you more flexibility setting up your gun for different types of prey.
Cheers,
Claudio