To try and help, if you have not noticed already we do not have many truck camper specific club members. But we have a lot of club members with Sunline travel trailers and some 5th wheels.
We can help suggest ideas that you can build off of, as the travel trailers etc are built using a lot of the same methods as the truck campers as that was how Sunline did it. And we have done a lot on fixing the travel trailers. But we need more pics to go off as to what you have.
I can see this much by your pick. That jack post does not look to be original. I might be wrong, but it does not seem to fit with Sunlines manufacturing of the time. A prior owner may have made that stand and support.
We can see the siding giving way as there is not much left inside that area to support the stand. If there ever was.
I can help with this much, it is not hard to take the siding corner molding off and undo that bottom piece of siding so it will pull back about 2 feet. The siding is installed from the top down. So taking it off, you start at the bottom and work up. If the wood is rotted behind the siding, you may be able to repair it and then put the siding back on and put new butyl tape in the corner molding that I'm sure needs to be changed anyway.
If you find the wood not rotted, then that location may not have been intended by Sunline to ever be used as a jack stand point.
We have lot of pics of how corners and siding come off and go back on.
If you come to that, let us know and we can link you to some pic of the process.
Hope this helps
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
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