C-Channel question?

[madpiper]

Hey, were newbies that are in love with our 1988 Excella, we call her Maxime. My wife is very sensitive to mold and we had some leaks where mold had developed in the front area on both sides where the main seam joins the front curved section. We are learning from the forum and hope someone out there has some experience with our problem.

Question is: How do I raise the shell to take the settling out of the C-Channel?

When we removed the bad section of the old floor we found that the shell has settled in three places causing the c-channel to pinch there where the shell meets the C-Channel and the frame (or the frame outriggers). We also left in all the old sub floor screws (instead of cutting them out) that were found in the C-Channel. We read on the forum to do this because some go from the frame thru the C-Channel into the wall support. That was a job cleaning out the C-Channel! Our old sub floor was 3/4 inch OSB that appeared to have been routed down to 1/2 inch everywhere it tucked into the C-Channel. In one place the shell had settled to as little an area leaving only about an 1/4 inch (collapsing the gap) in the C-Channel.
I've read on the forum that some type of truck screw jack has been used before with this type of problem. I don't have any truck jacks but do have transmission screw jacks that probably do the same job.
If I use my jack where do I brace it to the ceiling so I have an effective jacking point and don't tear up my ceiling interior?

Question 2 is: How do I install the new sub floor into the C-Channel past the old screws and get it between the pinched shell sag where the frame meets the C-Channel?

I plan on using Nyla Board to replace the sub floor (already ordered and learned about here on the forum) and will treat the visible frame with por 15. The frame is really in good shape with minor surface rust so I don't think the leak has been going on long. I pray that the rest of the frame is in as good condition but have no need to tear up any more floor at this time just to confirm that assumption.

If anyone has advice or suggestions it would be deeply apperciated! The sooner we get this fixed the sooner we can be back on the road.

[madpiper]

These photos should show the problem with the C-channel gap. What is the best way to put the new floor board (Nyla board) into the channel where the C-Channel gap has shrunk?