I changed the shelf material on my Widow today. The old calf hair was pretty worn and I wasn't sure it was doing its job.The bow shot fine mind you. I replaced it with Velcro. Did a damn good job cutting it out I might add. I even put back the little piece of whatever it is the Widow boys stuck behind the strike plate. Anyway, my arrows are flying low left now. Any advice would be appreciated. Any advice would be great. Tony Z

Right or left handed shooter?

If the bow is right handed I would guess the calf hair was a tad thinner than the Velcro especially if you used the self adhesive stuff, I would peel it back just far enough to remove the added side plate spacer and try that.

Right handed. Thanks guys.

Rick welch has a tuning method to explain this but I cant remember correctly, someone will chime in.

I was shooting left with my KMag ever since I bought it (right hand shooter); replaced the plate and shelf and it fixed the problem. The shelf was definitely thinner and I can't remember on the plate.

I'm gonna shoot some more after work today. Maybe my form was coming apart because I'm looking for a result of the change. Don't wanna dig through the garbage can for that calf hair ! Thanks guys. TonyZ

Motorhead hit in on the head, no pun intended.

There is a great chance that the thickness of the velcro is greater than the thickness of the calf skin.

A trick to helping arrows out that are too weak is to thicken your strike plate, moving your arrow farther away from center.  I have done this quite a few times when getting a bow set up and don't have a heavier spined arrow on hand.  

Use a thinner strike plate, or remove what is behind the strike plate, and your problem should be solved.

Velcro is thicker than calfskin and that can stiffen things a lot.Even 1/16" will make a noticeable difference.You may want to think about going back to calf skin.

also...( I no longer use velcro for this reason...though many do)...

Be sure the tips of your feathers are "snag free"
Velcro is a bunch of tough loops that by design love to get snagged on things.

..I use "Bear hair" for this reason since it isn't looped..

messing with the shelf material is such a big deal people don't realize how much it effects your arrow spines.

try a piece of a paper match stick behind the strike plate its pretty much for when you touque the bow a little it gives a little pivot point so you don't bump the arrow at release.  

the shelf is different the velcro might be too thick which in a nutshell lowered your string nock so raise that a little or trim down the velcro which like others have said it snags the fletch  when its left un trimmed.

I get the super thin shelf material that 3 rivers sells and use that for both the shelf and plate I don't use anythign behind the strike plate so I can address those torque problems when the show up not hide them but thats me I just can't do that to everry bow i have.

yes, go back to what you had . the Velcro is a lot thicker.

Really has little to do with thickness but more to do with velcro being a more giving (cushoning) material.  Bear rug rest on side plate is even more so.