Update:
The trays aren't working at all. This is explicitly a portable kit, so I have been out and about with it over the last few weeks:
-Alternator on Nissan Quest
-Timing Belt and water pump on Honda Accord
-Shocks on Ford Explorer
-Brakes on Mazda Miata
-Starter on Subaru Outback
The tools themselves have been amazing. Even breaking the crank pulley bolt off of the Honda only broke a couple of extensions; the breaker bar and extendable ratchet worked wonderfully. The only thing the 3/8" was used for was the spark plugs.
But whenever I take them anywhere, they arrive in complete disarray. Even with all of the 1/2" sockets in the bottom, the box is top heavy, and so tends to tip over. Even without that, though, any kind of sudden stop (say, when a truck pulls out in front of you, which happens all the time around here) will cause them to roll around and get mixed up, especially the 1/4" set.
I was going to try to make new, deeper trays, but my experiments have been disastrous; plastic is either too stiff and doesn't expand, or is too thin and breaks.
I would try foam, but I really don't want to have to cut out 120 slots (240 if I use a double layer) to fit the tools into.
I am looking at rails, but seem to be having some issues:
-My 1/4" set has 10 each SAE and Metric in both shallow and deep. The only problem is that the rails are longer than they need to be, but I suppose that I can cut them.
-My 3/8" set has 8 shallow SAE, 8 deep SAE, 12 shallow Metric and 13 deep Metric. Starting to be more problematic, but this is still doable; the 21mm deep might still be loose, though. At least the length is about right, although it will be tight.
-My 1/2" set has 13 each SAE and Metric, but only in shallow (I have some 1/2" deeps, but they stay in a different box, with my impact gun, as they are generally for lug nuts, and so those are the sizes I have: 17mm, 19mm, 21mm, 3/4", 13/16" and 7/8", along with 32mm and 36mm axle nut sockets). Worse, their combined length, especially in SAE, is longer than the rails that I can find, even the ones with 13 pegs.
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This is why my original spec was for a cased set; I'm not exactly regretting it (I got some amazing tools for the money, and spent it more slowly, which helped), but this is a problem that I really need to solve.
Any suggestions? Or should I just bite the bullet and spend the weekend cutting slots in foam?