We have two indoor tracks within 2 hours drive and one is about 105' x 60' ish and the other is probably about 90' x 50' ish and we race 1/8 scale on them all the time!!!! Sure the track is tight but it is still fun!
The larger track is in an 80' x 200' building and the smaller is in a slightly smaller building.
Can't wait to run electric this winter though!
Hope this helps.