remember that the oil making it to the filter is going through a hose that is about the same diameter- Then it pressurizes the oil filter canister- then goes through the filter and exits through that hole. It works fine that way- they were never meant to move a lot of volume- they were meant to keep the oil moving and at 15-45 psi- the reason the cartridge is so large is so that as the filter began to clog there was enough surface area to stop any possible restrictions that might starve the engine for oil. that is why there is a gap between the outer wall of the canister and the oil filter. the oil does not filter through the entire surface area just the least point of resistance- as it clogs that point moves.
I change my filter about every 3000 miles on the truck- I am anal and change my oil every 1000.
you would not get much benefit from enlarging the hole-
The hole where the oil leaves the pump to come to the filter and returns to the engine would not change in size- they are both 1/8" Female pipe thread- the orifice on those is roughly the same as on the hoses- so to really make a difference you would have to drill out those holes and re-tap them to a larger size- as well as the hoses and the fittings on the canister- so the enlarged exit hole in the filter would still hit a small hole as it leaves the filter and as it goes back into the engine. might get a little velocity increase, but they work fine as is.
You could be a little slow like me and hook the hoses up wrong so that the fill line goes in correctly but the return line comes out the drain rather than the return and nothing gets filtered for the first thousand miles until you figure it out in a homer simpson moment.
