I had planned on installing the stock 26 G grey tank. I was under the impression that It was mounted in the center, but forward most section under the dinette. If the grey tank is centered as I thought, then it won't throw off the side to side balance.
I will not be installing a hot water tank. However, I was under the impression for some reason that you can't really get the water out of the water heater under normal circumstances unless there is more water to replace it? Thus, it doesn't actually increase water storage. Again, I may be totally wrong about this, its just what I gathered from someone's else's post.
I'm not to worried about the 20 gallons of fresh water in the back. It's only ~64lbs more than the newer 12G tanks that Scamp
now uses. The additional 8 gallons will be in front of the stock position. The tank would also be pretty much on the center line of the side chassis rail. I plan to use 2 big batteries on my tongue, that will help counteract the water in the rear. Lots of people here seem to make a big deal out of extra on-board water throwing off the balance and towing. I'm not a super experienced "tow-er" and could well be wrong, but I'm inclined to to think that an additional 60-80lbs of weight
(whether even of uneven) will not make a big difference at all. With tongue weights yes, but otherwise I don't think it's big deal.
That said I have always tried to pack my trailers with weight
distribution in mind- but I don't stress it.
I have considered using a 10G tank under each dinette for better SIDE TO SIDE balance. I Haven't ruled it out yet, but I'm not to crazy about doing that way. It would be nice not to have the underwear storage so broken up under both dinettes, plus 2 tanks to drain and fill is just more to worry about.