my friend has a warp feed on his eMatrix, so i'll try to help u out on this one.
1. i believe it's around 1-1.5 lbs without hopper.
2. i've held my friend gun before when it was loaded with paint and everything... and didn't notice it being side heavy. technically, it would be a little side heavy, but it wasn't noticable to me.
3. no not really... it may take a little getting used to when u first use it.
4. yea, i believe so. i think i saw a few pics of cocker with the warp feed on it (it wasn't an STO tho).
hope this helps.