Rod, after linking back to earlier LM317 threads there is the dangling participle of isolated AC vs. DC ground. Does the 3-D rendering function allow you to "install" a 2-cent 1N400x diode into 2 of the 4 bridge pads (AC to +) and, say, a jumper wire between the other 2 bridge pads (other AC to -)? This would allow the same board to be used for 1/2 wave rectification where the AC and DC grounds would be the same which can be handy in some rolling stock applications. This can also be handy in track-side applications making it directly compatible with insulated-rail triggering.
Separately, I may have missed it but I didn't see discussion of using the LM317P insulated package which would allow you to bolt the LM317 directly to the chassis/frame from heat management.
That is, finding those insulating washers and related hardware pieces can be a nuisance. The insulated package is harder to find but can be expedient albeit at a price. You can't get a whopping deal on eBay as you can with the LM317T (metal tab) for less than a dime. While there are several eBay sellers of the insulated package, this may be the rare case where buying from DigiKey is cheaper!