I checked GandRtactical (listed tangodown 7").  Globaltactical, couldn't find a link. Adco listed the tangodown and a few magpuls.  Where do you guys get em?  Which kind do you like best, ladder type, panels?

There aren't any current KAC/TD type "hard" midlength rail panels, though I begged the guys over at TD to make a few. (Jeff).  Understandable, though, since the demand wasn't there from their #1 Consumer of these; US Mil.
The only stock mid length rails are those made by Falcon, and they are ladder types.

The type to choose is all personal preference.  I prefer the hard, panel cover, type.
If that's your case, its a relatively easy prospect to cut and trim 2 rails into mid length size w/ a lil' TLC you can actually shape the second panel around the 1st to look like 1 continuous rail cover...

/S2

SULACO is exactly correct.  I've taken TD panels and trimmed em' so they butt up to each other and you barely see a whitness line once they are installed.  It ends up looking like a one piece panel from anything more then 12 inches away.