The 2007 T257SR is a larger capacity camper then your current T-2475 by the brochures. The 257 will allow you to put more cargo in the camper which can be a good thing if room and cargo is a need.
The T257SR is a 7,000# GVWR camper with a dry weight of 4,930 or 2,070# of cargo above dry.
The 2004 T-2475 is a 5,500# GVWR camper with a dry weight of 4,825# or 675# of cargo above dry weight. And that sounds odd for Sunline to size this camper that low on cargo capacity but it may be. I took that from the 2004 brochure, is by chance that a typo and your T2475 a 7,000# GVWR?
Point being there maybe an effect of the maybe a larger camper on your truck. This may or may not be a problem, just mentioning it to check it out.
That is a nice camper. The slide system of that era was good and well proven. But check the slide roof and floor for soft spots if you have not. If this was on a seasonal site, owners sometimes leave the slide open all season even when they are not there. That is not really a good plan.
It sounds like you tried the moisture meter and things have come up good. That is a good start. Good for you!! At the moment it seems it could be a good dry camper. As John mentioned, how was the roof condition? Did they keep after the caulking? You should be able to see if they put any new caulk over the original and would expect it to be touched up on the caulking. If they did nothing, be prepared to deal with it when you get it soon so you can keep it dry.
Other then the roof shape, slide condition and added weight potential, that camper sounds good for you as a sise upgrade.
Hope this helps and good luck. Let us know how you make out.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club