my bud gave me a set of mag arms. i gonna try them in my sons 670, it has the usual mods (501 , y-pipe, boots , thick gasket, head cut.) what would be a good spring to try with the mag arms? i`m gonna try 287 ramps first. and try and be around 22 grams on the pins.any one use mag arms in ther 670 or am i wasting my time.