There is no question that the Comanche series is structurally stronger than the Cherokees.
There's probably no better demonstration of this than Max Conrad's 1959 flight from Casablanca to Los Angeles, a distance of 7,668 nm. He took off in his Comanche 250, with its 2800-pound "maximum" gross weight, at an actual gross weight of 5,000 pounds (179% of "max"), with 520 gallons of fuel on board, nearly nine times the stock Comanche's fuel capacity of 60 gallons. (ref: Flying magazine, Oct. 1959.)
Do you think you could pull the power back far enough to get down to 10 GPH from 14 GPH? I wouldn't mind slowing it down for my time building when i needed to go slow.
Sure.
For example, since there's not really anywhere to go when flying these days, I decided to keep things more interesting by doing some tests with my Mooney M20R yesterday. Normal cruise for me is 170 knots at 12.2 gph, at 65% power, lean of peak on my fuel-injected, 280hp Continental IO-550. Fuel injection is an important ingredient to running lean of peak, and lean of peak is important to getting fuel flow that low, which is why it's developing more power at lower fuel flow than the Lycosaur O-540 from the Comanche.
I verified my speed with a four-course box and then I stabilized it at a couple of lower power settings:
At 12.1 gph, I got 170 KTAS.
At 9.5 gph, I got 150 KTAS.
At 7.9 gph, I got 137 KTAS.
I got the flow down to 7.1 gph at 14" MP and 2300 RPM, but while it seemed to initially stabilize at around 110 KIAS, over the course of 5-10 minutes it continued to pitch up (autopilot was in altitude hold mode in smooth air to keep things as stable as possible for the test), and at around 100 KIAS the prop hit the flat stop and the RPM started to drop slightly, which resulted in the power decreasing further and the pitch-up accelerating, so I was ever so slightly behind the power curve at that point. Fuel flow dropped to 6.9 gph by the time I increased power to try for a speed that would remain stable.
But, that shows you that it's easily possible to knock 1/3 of the fuel consumption out, so you should be able to get 10 gph on the Comanche 250. You'll get better mpg as well - For me to get another 10 knots of speed above my normal power setting, it costs me another 5 gph. That top end speed/power setting is very costly, and you can get some pretty significant reductions in fuel flow for relatively minor loss of speed.