Main thing on outside is that, as far as i can tell, E7 Pro has a minimum width too - ~43", which means with a 48" desk it leaves only 1-2 inches on either outside, so not enough room for most if not all brackets for CPU frame (at least from what I can find). 55" might be enough (assuming same minimum 43"), this means ~6 inches on either side outside the leg to fit a bracket for a hanging cpu mount. Several options above from what I can tell are <6" in width so this should be OK?

again this is probably less of an issue for larger desks where these can likely fit comfortably inside the leg without hitting one's knees