Another Bed Cover Question - Side Rail Height

I have an '09 Taco and am looking for a hard bed cover. I have searched past threads. One thing that concerns me is the difference in the height between the side rail caps and the tailgate cap. I am llooking the the Extang Solid Fold Cover. The dealer test fit one on my truck yesterday but it left a big gap between the tailgate and the cover. He suggested putting some extra sealing foam on it but that seems like a bit of a cheesy fix for a $700 cover.

So how are you guys dealing with the height difference in the caps?

I also like the look of the Undercover brand that the dealer carries but there is a bit of an advantage to the folding cover.

 

I have a Bak Flip G2. It had a gap at the tailgate. I called Bak Industries about the gap, and they sent me a couple of different rubbber seals to try. The cover comes with a thin rubber seal. I peeled the old seal off, replaced it with one of the new seals, and it works great.