put 4.5 rivets in both holes on the stock 8dn20 weights, use a white/white/white yamaha primary spring, get a helix like 50/44, 51/45,52/44 and use a green dot Yamaha sec spring set at 60-70 twist, that will wake it up nicely. I listed a few helix that will work, the 50/44 would be my first choice, the others in the order, the 52/44 would make it a little more aggressive upshift(quicker) but all will backshift nice for on and off the gas in the turns and trails.
youll only need 3 of the rivets if stock as the srx comes with 4.5 in the outer hole already, if..... its not been messed with.