Thanks, Paul and Tom, for your replies.

Paul, I like your approach. The only thing I might do differently is
to brace the top with 2x4s from side to side just outside of the
bulged area, so squeezing at the lift strut attachment area has places
to react against. I'll give this a shot as my first step.

Tom, I wasn't aware that there was a repair kit thanks! I'll
definitely write to Spindelberger and get details, although I'm leary
that the worthless dollar will make it very expensive to buy and ship.
Formed reinforcements would definitely be a long term solution to
deformation. One question - did the bars mount fore and aft, or did
they go from rail to rail?

-John

On Jun 29, 10:42 am, 5Z wrote:
I had a trailer of that vintage and sometime around 1990 I got a
repair kit from Spindelberger.

It consisted of a couple of aluminum bars perhaps a foot long that
were bent to fit inside the trailer and stiffen the bow near the lift
struts. I used a come along to squeeze the trailer lid to a specified
width, then drilled and installed the stiffeners on the inside. That
did the trick to straighten the sides.

So, contact Spindelberger and get the repair kit.

-Tom

On Jun 29, 10:30 am, sisu1a wrote:
John, instead of a come along, try using a bar clamp. Buy the type
that you mount on your own galvanized pipe so you can get the span you
need. Use more than one if the area is large. Remove the struts and
place short pieces of 2 x 4 in between the clamp's jaws and your
trailer top. You will probably need to bend past the straight-line
point, so it can "bow" back straight(ish). You may consider installing
some aluminum flatbar lengthwise over the weakened area to keep it in
shape. Good luck!

-Paul