ORIGINAL: 64years old
I have a history of asking why ! I'm new to xbows.8 days experience. My used bow had the string about 1/8" above the rails , thats with riser firmly held in place. The top of the nock and the top of the string were on the same plane. I shimmed it down to just a paperthickness above the barrel. If you are just above the barrel you can measure..if you contact the barrel you have no idea of what downward pressure is exerted on string. When I shot the bow with the original clearence it shot very well....maybe it will shoot better. I like the technical side of things...help me continue this forum......???how long should bolts be , how far past the rail ?? 64
IMHO, length is not as important as over all weight. I've found 20" to work best in my Excals, had some 18" made up and accuracy suffered.don't know beans about your bow, but would think you would be ok w/ 20" about 420 gr minimum.
edited to add: all the xbows I've seen have had string tight to rail. Don't thiunk you will gain anything useful by shimming yours off the rail, but just my opinion, nothing more.