question

Cabble gage is already very large, smaller maybe.

But I found that Victron must be aware about this problem since they are selling WireBox to fix it.

"Victron Energy MPPT WireBox-M for 100V 30/50A & 150V 35A BlueSolar and Smartsolar Charge Controller"

So you need to plan for another 30USD to have proper connection.

I am surprised as their product are already quite expensive, I hope it will sustain very warm temperature properly, beside this weakness in connectors (quite hazardous) I am satisfied.
If you fix it on a wall and never touch it you may never notice that it does not take much to disconnect the cables even if the screws are tight, but in an RV it may be a different story.

One additional comment, while I am spending time here, I do not recommend "Victron Energy BMV-712 Smart Battery Monitor" since it it not much more accurate then a 40$ one, I got fooled in thinking it would be by a support engineer at Battleborn, you need to charge them to 100% regularly else the estimates are off.