Morning Afroman1, It all depends on if you can keep them trained close enough, another 300watt LED, wouldn't hurt anything except make your tent a few degrees warmer, as for height, usually start seedlings at 24-28 inches, then a couple of weeks later you can lower it to 14-18inches.
GoodLuck Afroman, if you need any help feel free to ask, lots of good ,friendly help on GWE,
and Welcome to GWE.
PS- another light will help to make your buds more dense,hard.