You mean something like this...
I (we) did the exact same thing you are asking about. We removed 4"/side to fit between the mini-tub. The only negative is that it took the tank's capacity from 18 gallon to ~10. Getting only 8-10 mpg it SUCKS for long cruising. I've driven it this way for more than 4 years and have had NO issues.
I am currently having a friend that is a fabricator make me up a stainless tank that is approx 4" deeper but the same width for additional capacity. As well we are putting the baffles in and installing the A1000 pump in the tank.
Hope this helps.