We stayed there once, we really enjoyed it too.
Admittedly we were lucky, up to the day before we sailed tents were blowing down in the storms, but then it clamed down & ended up the best week for a long time. 
It's not at the National Sports Centre this time tho', it's on Bray Hill.........but not in the road, thankfully!
read about it here -
https://motorcyclesports.net/metzeler-tt...of-man-tt/