bulkhead questions need some help

[ghost_pit2001]

heres the problem i have,2 - 1 1/4 holes and 2 - 1 3/4 holes

if im not mistaken the 1 3/4 inch holes are for 1" bulkheads which from my calculations are only good for 1200 gph
1-the return holes which are 1 1/4" would be what size bulkhead?

2-does this seem kinda small?

i idealy wanted to turn over 10x the water and use a smaller pump to run
a polisher and another source carbon etc. and what not at a much slower rate say 3x.

3-how would i achieve this with 1" bulkheads?

4-also i looked at the flow charts and came up with a pm27 can anyone cross this to reefflow pumps?

 

[KaiserSousay]

if im not mistaken the 1 3/4 inch holes are for 1" bulkheads which from my calculations are only good for 1200 gph
1-the return holes which are 1 1/4" would be what size bulkhead?

On factory made bulkhead fittings, I really can`t be any help.
Never used them. I always used PVC electrical conduit fittings with rubber washers for my bulkhead fittings.
With what I have always used your 1 ¾ holes would let you use 1 1/2ID for your drains and 1ID for your returns.
Not much help if you use factory made bulkhead fittings though, but it might give you the flow you are looking for.