I've seen some that don't have any angle and the one's that do I would say maybe 5 degrees. I'll have to dig around in the garage and see if I have a set an let you know.
the center of the block should be at 4" then. each side(front to back) should have a 1/2" diff. each way. I dont know what the degreee is but thats what my buddies blocks were.
get 3" and be safe. Dont be stacking em! I could go snap a pic of my 3"....and my plates are decently close to the ground...I clear but I wouldnt push my luck any more
idk bout that man thats alittle iffy. id just stack two 3"s together and make a total of 6". a 6" block is about as far as i would go....lol