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An overrated (within reason) WDH can be used in many applications as long as they are installed/adjusted correctly.
IMO a 7,000lb GVWR TT utilizing a WDH rated at 1,700lbs would not be my recommendation. Worst case loaded tongue weight would be 1,050lbs (15%) if the TT was loaded to it's GVWR.
I personally wouldn't want more then a 1,200lb rated WDH for a 7,000lb GVWR TT...., a 1,000lb rated WDH would be ideal especially if your loaded TT weight tends to be in the more common 6,000lb to 7,000lb weight range.
Bob
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2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)