How many holes and what size did you drill out?
I drilled 20 holes on each side that are 1/2" apart using a 1/8" drill bit. All of the pvc is 1 1/2". I have a ball valve before the return and also one before the fountain head. I leave the return wide open and still have plenty of spray when I open the fountain wide open. I can also start closing the return and it will spray over the far side of the pool.
Works out great in case the kids want a small fountain or a large fountain spraying around the middle of the pool. Lots of range depending on how you adjust the valves.
24x54 ABG 15,200 gal, 22in Ecco Sand Filter, 1.5HP Ecco pump