Yeah, it fine! If you skimmer can filter more water than what goes through the sump in a similar time, it is similar to a recirculating skimmer and is often extremely effective. Now if it is so large that it completely removes all organics from the water then, keeping a head might be difficult... but more of a bioload might help What is the skimmer and pump and what is the return pump. Also not that skimmer pumps, because of the air pull do not often match the water per hour rating that they are often labeled. Most folks oversize their return pump anyways... I say it is best to have the return/skimmer pump as close to equal as possible and if you are going to tilt it, have it so that the skimmer is the bigger player.