I would make sure i was happy with where the tank was going to be. Then i would cut access to the basement that would allow a straight drop from the bottom of the tank through the floor. I used 1 1/4" return and 1" drains. i cut five 1 1/2" holes with a spade bit through the hardwood floors making sure that i would not hit the floor joists before i placed the tank. with the 1" pvc these holes were great but i had to ream out the one for the 1 1/4 pvc and add a notch for the control wire since i wanted the pump control in the stand. Five holes were one each for the Bean Animal drain, one for the return and one for good luck and so that i could run, maybe, a water change hose or pipe in the future. with your plumbing perhaps a jigsaw might be a good idea, just cut a rectangular hole through the floor inside each end of your tank stand. I am a believer in vertical drain plumbing from the tank to near the sump. this drains better than elbowing just below the tank. use one drain for the siphon and put a gate valve on that one. For the return i would suggest using 45's; are you planning to run a manifold off of your return for other equipment and functions, or add other pumps for reactors, UV, diversions, etc.? I would put a section of flex poly hose above the pump, valve then 't' off to another valve for future reference then '45' above the 't' add a 't' on the angle aim the resulting 'v' toward the corners of the tank stand and add 45's to resume the vertical to the returns on the bottom of your tank. either run 1.5" up to the tank or drop to 1" at the 'v'. 45's will reduce the flow loss.