This has been an ongoing issue for the Sport classic, MS and Monster.
Heat cycling of these tanks will expand and contract as much as 1/4 inch under sunlight and or heat from the Bike.
This will cause some deformation.
It is really hard to pinpoint why plastic tends to deform over Steel, aluminum, or fiber
If the tank is removed and washed out and left out to dry or have air circulated through it. We have found the Sport classic tank will contract or shrink back.
Can take anywhere from 1 week to 2 months.
It is almost like a lifeform.
Caswell is only as good as the prep work to install it. Prep is 95% of it.
It is also a tool used to "extend" the life of the tank and not a cure. Expansion may still occur due to heat but can help with reinforcement to keep the shape. It will help with keeping ethanol from leaching it to the tank surface to cause bubbling or pimpling of the paint.
We use a special rotation machine and special aggregate to rough up the inner surface for the epoxy to have something to attache to.
See here for loads of info
Out Of Warranty Spreading Tank Problems
The service we offer cost $400
If you can get a new tank I would coat it right away
If you can find a good used that that has shrunk back or decreased in swelling it is a good idea to coat it. If you plan to repaint cost it first then have it painted.
If it has been painted or has stock paint we can protect it.
I've heard of guys lining the inside with caswell? I had an 07 s4rs white/red. Wish I never sold it.