R Leo has towed more 3500lb parts cars behind his wagon than any of us could imagine. You might search "tow" with him as the poster to see what his experience is.
Also, having had RV's, you always cram them full of stuff, and add quite a bit of poundage to just what the trailer weighs...........

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John