Forward fish box drain (Update)

[wattaway2]

Others will likely have a better idea but my thoughts go to going from the center of the drain well assuming it's still there and doing a very small pilot drill bit out ward . You can the take a PC of coat hanger wire and run it thru to check your alignment. The inside box and the outside should be very close in there alignment already but you could check you hole and adjust it from the outside within reason