What are your tips and tricks to prevent rubbing the hair off in the loin area? I thought I had it figured out until the winter coat grew in this year.

I would use a 28" long saddle pad. Never had one rub with a 28. 30 is standard , 32 is like larger roping style. 

May I ask what saddle you are using? I have a hip high short backed horse and I feel like my Meleeta Brown and Wanda Bush saddles are too long for a 28 inch pad. 

Have you checked saddle fit lately?  your saddle could be bridging and wearing the hair off. 

I'm using a treeless so it conforms to her back.   I only started having issues when winter hair came in.

For daily riding I use a round skirt Bob Marshall. Its the only thing I have found that doesn't sore her. When I barrel race I use a Seven saddle. I've just got this saddle a short time ago so time will tell if it will work.

Also, a 28 is too short for the BM since that is 25" long.  It would prob work on the 7 because that is only 24" long.

I initially rode her in a Thinline with the real wool so it would cover that area with no issue. I think I'm going to have to go back to that. If that doesn't work not sure what I will do.