We've double towed on a few previous rigs. I fabbed the receiver hitches and ran the wiring. You can only make things better since what comes as OEM leaves a lot to be desired. Longest rig was 82' front of truck to back of boat. All within weight limits, but over Louisiana state length. But, like the OP, I was only going to the lake not too far away. The shorter double tow was a little over 70' I think, and we went multi states like that. Everybody has their own comfort level so I respect whatever everybody else wants to do.
My personal opinion, with the 377, I probably wouldn't. Boat is a little on the heavy side even with a light tongue, plus the length would be a little too long for me, and even I like to push the limits sometimes. Could it be done, sure, provided the receiver hitch is done right.
Warranty, I have my opinions that I get barked at over, but oh well. As I said before, you can only make the OEM stuff better. I've welded in a few places on our new rig when it was less than a year old. If something breaks, I'm going to fix it anyway, better than LCI would. If you looked at all the stuff I've modded on ours, my warranty was probably out the first week. But, it's ours, I want it like WE want it.
John and Rebecca Dickson
Emma-8 / Little John-5 / Iva-1+
2013 Ford F-350 Lariat FX4, CC LB PSD, DRW
2015 Jayco Jay Flight 28BHBE (#8)