Taken you have done your homework and know the capabilities of your truck and combo for sure.
All the axles seem to be 7 or even 8 k rated are they not? This is a non issue.
Where I have sMe truck as you do you think the triple is better at 39.8 feet?
I found an XLR at couches like you suggested and it has triple and only around. 2200 on pin,.
The local dealership has my attention pm the voltage with dual and 2550 pin.
I also have to consider dollar and our crappy CDn dollar at this time.
I want to decide soon and sell my cougar ( not wife!!!)