Rear brake problem?
 

I noticed a significant decrease in stopping power when in reverse in compared to moving forward. Does this indicate a rear drum issue? Front brakes are disk.

They may just need to be adjusted. They should have self adjusters but they could be stuck, froze up. The adjusters work when applying the brakes in reverse. Back down the driveway and hit the brakes hard several times, that may free them. If not, time to pull the drums and see what's going on inside.

The brakes typically don't grab has hard in reverse as they do in forward. The lining on one shoe is smaller than the other. Not positive but I believe that allows the shoes to pivot more in reverse and actuate the self adjuster. Also means it won't grab as hard in reverse.

Modern brake shoe system is designed to be "self energizing" and basically work much more efficient when the vehicle is moving forward.

Sounds good. I'll give that a try.