Need to Fix my plumbing issue

[spikehs]

I have a problem w/ the plumbing on my tank (36x18x18) ... For whatever (brain fart) reason when I got the tank made I got two holes drilled, which can only accommodate 3/4 tubing. Its been a year and I've managed to get away with it, but I have to have my flow waaaay down and even then It provides barely enough flow from the sump. I actually caught a flood in progress as some algae had restricted the flow on one of the tubes.

Anyways, I am looking for some ways to upgrade my plumbing to increase the flow.. About the only options I can figure are

1. Add a HOB overflow, i'm not wild about this as their reliablitiy always seems iffy to me

2. Take tank down, and get an external overflow added (the stand I have wont accomadate an internal one)

3. Add some plumbing bits to increase the diameter of the tubing after the bulkheads... although i'm unsure how much this would help.

Basically just looking for some ideas/advice. Thanks!