The fuel in my cforce 1000 overland gets HOT during a good long ride, like hot enough to really pressurize the tank.  The rear of the atv is hot enough to make the glove box below the rear rack uncomfortably hot to a hand rested on the floor of the box. 
Is this a problem or is there no reason for concern?  The tank sees enough pressure to leak out the gas cap.  Relieving the pressure and reinstalling the cap will still build up enough pressure to bleed out.  I'm worried about the tank's ability to live a long life here and it'd really suck to have a blown fuel cell 10 miles back.
Thoughts?

[2015 Z Force 800 53/Trail EPS]

Heat..that is heat from a source like the exhaust pipe and muffler that collects enough to noticeably effect area parts and actually heat fuel in a tank is always concerning. It really shouldn't do that. It's bad enough riding in hot enough places that that heat effects the fuel, let alone enough to boil the fuel and push it through a sealed cap. That could split the tank and dump fuel everywhere causing a fire...and you don't want to me on one that the tank gives-way..trust me. I would be very concerned and would take whatever steps I could to insulate the heat from everything else. There are a number of stick-on heat shielding that are effective. You may also want to wrap the exhaust as much as possible and build your own steel guards where possible. 

My 2022 800XC ran REAL hot.
627 degrees before my thermal heat gun flashed out directed to the area around the cat - that WITH the body panels in place and heat shielding.
It would leave a scald mark on my leg under clothing.
So it is recommended that you have your ECU tuned for it, but I tried one of these on it and it works great.
It is year specific but the 2nd GEN 800s and 1000s share the same basic components (block, head casting etc)
It was pretty straight forward to install and didn't take a heck of a long time.
It came with everything needed to correctly install and uses factory hardware and mounting points.
I am running the MSC 90 degree elbow as well - one of their better products.

https://rjwcpowersports.com/products/cforce-850-1000-header-pipe

Oddly my 2023 doesn't run near as hot, so I suspect the tweaked the factory tune a bit.

I spent a few bucks on Amazon and got some exhaust wrap fiber.  While I have yet to take a good long ride to really test it, I can honestly say that the quad is quieter (a major plus, I was surprised at how loud it is while riding) and the heat hitting my leg is reduced a bunch.  I'll update when I know the effect on the fuel tank.

[2015 Z Force 800 53/Trail EPS]

Exhaust wraps do a great job on holding the heat in as well as sound. The two most often noted down sides are that this causes the exhaust material to become much hotter which causes not only some material break down but far more expansion and contraction then designed for resulting in cracking on some materials over time. The other noted item was it also held moisture in against the pipe causing accelerated rusting on steel piping...which isn't a concern for stainless steel...obviously. A wrap is the only answer to many heat related issues though. Aside from re-routing its the only viable option open to us.

The fuel tank should not be building pressure. there should be a vent line , it may also have a check valve in the line. You need to look at a parts diagram to see where the tank vents.