any measurements? how much did you cut off?,..sounds like a good idea as I am looking for the cheapest route.
i tried to submerge a beer bottle (capped, in the sump after the skimmer) to see how much water it would displace, thus bringing up the water level, and the water level was no where near where I would need it to be to skim properly. (aprox. 3/4 inch too little)
Maybe I will try some large marbles in the sump. (before decide on cutting or not)
(reminds me of the story with the bird that drops rocks into a pot of water to raise the level so he can get a drink)