Pull through spots aren't really s thing on BLM land. You should be able to back in or turn around. It's very open just make sure you stay in a previously used spot. There's large enough areas for you.

There are several spots with plenty of room for a 19ft camper. Most of the area is pull through or pull off the road. FYI... It’s a very remote camping area on BLM land.

Probably enough room for a camper trailer. It’s all open terrain. I don’t remember any pull through spots specifically. But we were in a van so we weren’t looking either.

I think a 19ft trailer would be fine. Just watch the first few feet off the 89a into the entrance - there's a few feet dropoff that may give you trouble with a larger rig. If you stay to the SW of the entrance (furthest from Lee's Ferry) off 89a, the entrance off the road is much more level. If you go left at the fork at the research station, there are a number of large spots on the edge of the canyon that I believe you could turn the trailer around. "Going left" does have some rocky terrain, so go slow and take your time. No true pull through spots, but look more for clearings large enough to turn around. Enjoy.