This is the style pressure gauge others have referred to.
I have about the same MH and checking the rear tire pressure is a hassle. I usually end up just popping off the wheel liners and then checking the pressures. Our liners just pop off, while other liners are held on by bolts, which I prefer. I have used stainless steel extensions where the mounting brackets for the extensions, are riveted onto that style liner, without having any problems. With our style pop off liner, if you attached the extender to the liner, and your wheel liner pops off, you have some serious issues.
Be careful with those holes in the liners, the edges can be sharp.
