Ok pic heavy update.
Things have been slow from a build perspective. Spending a lot of time on jigs, templates and just figuring things out. SO glad I followed Bill's advice to go all the way through one cab first, then build the others.
Built a small parts jig using MicroJig stuff.
The jig at work.
Minor setback when momentarily set my router on the table saw then proceeded to trip on the cord and SMACK it went on the concrete floor. There were plastic bits that didn't survive and it wouldn't come on. Damn.

But thankfully I was able to mess with it and get it going. Just broke some plastic around the switch and it worked once I got it out. Thankfully didn't land on the bit and bend the shaft or something.
A wise friend once said; "Nothing ever fell off the floor".
Spent a lot of time figuring out just how I want to do the hand holds. Experimented around with several iterations on a router template. There may be better ways but this is what I came up with. Note using the Forster bit to remove some material really helps. If you've got a better router and better bit you might not need to but this helped with my wimpy router. I'm using a 1/4" trim bit with a bottom bushing so template has to go underneath the work.
The template is made so the edges is EXACTLY aligned with the edge of the top. Add a piece of 1/2" scrap when aligning with the back. The template cuts the hole so there's exactly the right clearance inside for the 1/4 round. I have a center line in the template that lines up with the centerline of the hole on the workpiece. I line up the template with clamps then mark the hole. Remove the template and use a slightly smaller Forster bit to remove some material. Clamp a sacrificial piece underneath to prevent blow out.
Realign the template edge & centerline and clamp it. Flip it over so it's on the BOTTOM. Screw it on from the top with flat head drywall screws and be sure the heads are below the surface so they don't interfere with the router. Now trim to the template.
Here's a hole rounded off with a 3/16" bit.
Test fitting the Top & Back to see how it's looking.
Then I realize I may not have left enough room between the handles for my NL4 connectors. So I check and it's really tight but I think they'll work. I had just picked an arbitrary distance (6" from the side) to center the handles because it looked good. Should have thought that one through a bit more.
If only I'd set the handles 1" each way to the side I'd have 2" more there and be fine. I'll probably do that on the remaining 3 cabs even though this one will be different.
My plan is to inset the NL4 connectors so they're just flush and put a backer behind that for the screws to go into. This is me experimenting with that inset and test fitting in some scrap. Again, using Forster bits. A 2" in this case for the inset and a 1" for the center hole.
There's really not much room behind panel #9 up in the top of the cab. But that seems like the most desirable (for me at least) place to put them.
Seems like I've been doing a lot and have yet to crack a tube of PL! Got a few more gluing jigs to make that'll fill the rest of today then (hopefully!) start gluing tomorrow.
-Dave