Why patch the holes? use them

the bigger hole is the supply, the smaller one can be used as a return/is a return.

meaning the holes need bulkhead connectors, PVC plumbing, ect then down to the sump.

PM me for more info, if you need to but the big holes are plumed to the sump with a length of pvc coming to the top of the tank aka trim ring height. I have 27" intake tubes on my 210 drilled.

Id sell the tank if you dont use the holes, but I highly recommend you using them, its pretty much the best filtration system for a filtered aquarium. Like I said let me know, I am building a 210 sumped now and also have a 3 other tanks sumped, only my QT tanks dont use sumps.

wet/dry sump or which direction are you going? salt or fresh?