Roll n Lock questions

I have had a Roll n Lock tonneau cover on a GMC truck before and I loved it. So now I'm thinking of getting another for my Taco and was wondering what the tallest item that would fit under the cover mounted on a Tacoma. (I ordered an ice chest that is about 18 inches tall). Also, was wondering if they use the bed rail or remove it upon installation. Thanks in advance for the info.

 

No responses here so I called Roll n Lock to get answers. So it turns out that the Roll n Lock takes up 1 3/4" from the top as a rule of thumb for measurement. So I measured the top with my OEM Tacoma bed mat in place and the bottom to top measurement is about 17 3/4". So anything less than 16 inches tall will fit with the Roll n Lock cover closed. (My ice chest will not fit).

I also asked about whether they use the rail system or not and they do. He said that they designed the Roll n Lock to fit and use the Tacoma bed rails for an easy installation.

 

Piggy packing off of a roll n lock thread so I don't start a new one.

But will a 2nd Gen one fit a third Gen? I tried to search but no luck. Are there differences in the width of the bed that would make this not work?
Tia

 

Jumping in thread with a ques, just picked up a used one and can't figure out how the key works in the lock to keep it kocked. If I turn it, the whole knob turns, is there a secret? Can't seem to make it lock.
I saw the instructions about 7 o'clock, 10 o'clock but that's just to hold in place or release. Any help greatly appreciated.