Thanks for the reply GHamby!
I'll be using an SAE J1127 wire, will be super careful to not damage the insulation as its being formed. Filing smooth any edge of the angle bracket(s) I'll be using to form the bend should keep it in good condition.
(FWIW Red cable of any flavor is fairly scarce around these parts for some reason---I have an on-line source if I can't find anything locally.)
The cables will be secured to the HDPE with suitable metal cable straps with the through-bolted fasteners secured from behind with T-Nuts. Most likely those will be further secured with LocTite #290 to keep everything snug.
Once this inverter assembly is completed the wiring will never be moved. Nothing will or should act upon them either except for the seldom used jumper cable clamps with their own Anderson connector. For that reason I'll further secure the mating connector to the HDPE too.