I've been backing boats since age 15 now 47 also backed my pop-up for years with that short wheel base. Fished local tournaments often had to back the boat a 1/4 mile down the center of the road becau...
I've found that if you can see the trailer tires, that's where the trailer is going to go... Sure, you have to make sure the rest of it is not going to hit anything, but if you watch the tires, that's the track it's going to follow..
Do this by looking out the window or the mirrors..
Practice is the main thing. Sounds like you have the backing down, just need to learn a new perspective..