I realize that this is an old thread, but just a heads up for those considering purchasing/installing their own slide topper.
The OP's problem is that he purchased the incorrect topper length associated to his actual slide length (flange-to-flange length)...., the proper length topper would have allowed the hardware in question to clear the outer slide flange.
All slide topper manufactures have a sizing chart, best place to start.
Dometic sizing chart:
http://www.makariosrv.com/content/EB...er%20eBook.pdf
In the case of the Domestic sizing chart in the prior link, note that the "Recommend Size" doesn't reflect the actual fabric length, but rather the fabric roller tube end-cap to end-cap length.
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)