Ive always been a velcro kind of guy but just got a longbow with a leather side plate seem to get cleaner flight? Anyone else?
I like to use a leather or calf hair plate on my longbows.Most longbows are cut to center of slightly off center.I like my side plate thinner then velcro,last longer and get better and more consistent flight.
In my experiments it depends on what the bow/arrow combination tells me it needs.
All other things being equal, the harder plate (leather) will move the arrow impact away from the side that the sight window is on. So, for a right-handed shooter, a harder plate would move the arrow impact a bit left -- and a softer plate would move the impact right.
Now, that is the result of my experiments. You might get different results. I do think that experimenting is worth the time it takes. Little things can make big differences.
The softer side plate changes the dynamic spine as Smokin Joe said. It functions in a similar fashion to a plunger. The difference, and it is a big difference, is that it lacks uniform consistency like a plunger has. You can't get the shot after shot repeatability and as it wears it changes as well.
A hard side plate with a well tuned arrow will tend to be a more accurate set up.