After a day of attaching and hauling tools and such into trees to hang screech owl boxes, I decided that some sort of suspenders were in order for my Tengu. I know there are saddle/harness sashes and suspenders available, but I found the Tool Rider GS Suspenders in my local hardware store for $20 and decided to give 'em a try.
They have a mini daisy chain on one shoulder strap (nice for clipping a couple of spare biners or the end of a lanyard) and a cell phone pocket on the other side. I like the sternum strap (like on a backpack) it keeps the shoulder straps from sliding off to the side when reaching or hanging in a less than vertical position. Gel padding in the shoulder areas makes these babies real comfy, no matter what I hang on my saddle. The model I got uses industrial strength clamp-type attachments like trouser suspenders, but if you already have rings on your harness, the GSX model offers swivel snap attachments.
http://www.thebrownbags.com/toolbeltsaccessories.html
I'll try them on my saddle for a while and report back if I like them. If they don't work out for tree climbing, I'll use 'em on my nail apron.