Are you sure you have enough clearance to begin with? You may need to move your prongs up to get more clearance between your fletchings and the shaft on the rest. Lay an arrow on your prongs and slowly pull it straight thru the rest to make sure they clear everything. You could also nock an arrow and try to eye ball it from the back. Increasing your rest tension may cause more problems than you are trying to fix. As well as making your nocking point higher than it needs to be.

Spring tension should be as light as possible and still hold up the arrow. When you shoot an arrow it pushes the rest down out of the way. If the rest is set to stiff the prongs will come back up too soon hitting the shaft as it exits the rest, throwing the tail of the arrow up.

Where your knocking point is to begin with sort of depends on the bow you have and what type of cam or cams it has. It should say in your manual where to start normally. You didn't say what type of bow you have. If you list the make an model maybe someone that has that bow or cam set up could tell you where to start.

I agree with the above suggestion if you are shooting a single cam bow without a dual track idler or something like that. My bowtech manual says 3/16 to 3/8 of inch I think. This is assuming your rest places the shaft level with the mounting hole for the rest, or close to it any way. If your rest puts the shaft higher than this, your nocking point will have to ge higher as well, and vice versa.

If your prong rest doesn't have a lot of adjustment to it, you may have to play with how it is mounted in order to get the right amount of fletch clearance and the proper height. You may have to rotate the whole rest up or down and then adjust the height on your prongs again. Sometimes you have to play with it a little bit to get it right. Other rests have an adjustment for the prong height, as well an adjustment for the whole carrier for virticle movement. Out of couriousity, what type of rest do you have?

One more reason why drop a ways are so nice to set up, but then they have thier problems as well.

Good luck,
Paul