At 15000lbs, the pin weight COULD be around 3000lbs, if loaded heavy. If you would be traveling light except for the GW, then might be able to do it.
Find out the rear axle weight rating (RAWR) on the 250, then you will need to know close as possible how much the weight on the rear axle is without the trailer on it. Rating less the actual weight gives you the amount left to use for pin weight.
Lots of 250s are towing 15k fivers, some are over on rear axle weight by a little and some by a lot.
One thing you should NEVER do is have more weight on the rear axle than the tires are rated to carry--and that number is around 7500lbs.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired