opnspaces, haven't been on here for a while so just saw your post. The rig now stops so much better that I don't have to use the manual lever if I don't want to. However I want to. I apply it very lightly to start slowing everything down along with the engine on compression (the 292 has a lot of it). I finally apply the brake pedal to bring it to a complete stop. Makes for a very smooth stop.
I primarily use the manual lever as my tow vehicle, being a 1965 Chevy Van, never had very effective brakes (plus its 49 years old). So I prefer to use the trailer brakes to help out the old beast, plus its cheaper to replace trailer brake shoes than the van brakes. Parts are getting harder to find for the '65.
Note - the van brakes have been completely rebuilt with new master cylinder, brake lines, shoes, springs and cylinders, so they are as good as they can get. I don't tow stupid.