I cut back to near 100 gallons to gain storage as well as replace aging tanks.
It's plenty except a few places on the lower River systems.
I just stop and buy fuel where its inexpensive.
Buying 30 to 50 gallons reduces sticker shock, gives me access to leg stretches, water, trash, etc...etc more frequently. Planning is just part of successful cruising.
No good designer is going to calculate stability on fuel tankage...it's a consumable, not replaced uness you ballast during the trip...not likely.
Funny, read engine threads and fuel economy and the mantra is fuel is one of the least costly issues in boating....
It will only hurt resale...maybe to some..good salesmanship can make it a plus. Especially boats never venturing past the loop or Bahamas due to age, etc....