Just got mine yesterday a put on last night (wasn't as easy as I thought)(will post a pic, do love them)....Should these fit very snug against my roof? I have a little gap between roof and support ends (about 1/4").
Machines

 

No they are raised up a little by those two plugs you put in..make sure they are set down in the track..

 

Not sure what plugs you are referring to????

 

I also had a little touble locking, using the lever....Thought I was going to bust it.

 

There are two plugs on either end of the base that have a 1/4 tallplug guide to fit down in the rail track to keep the whole thing straight on the rail..The cinch down levers will snap into place as soon as you are in the right place..kinda like a sweet spot..jockey them back and forth while wiggling them and it will cinch down properly.