Ok, forget the Q about the conditions, home dogs lined at +6.5 or +7.5.

It might interest you to know that home dogs lined at:

+7.5 is 9-17
+7 is 32-37
+6.5 is 33-34

This is from years 1985 to 2000.
Results from 2000-2003:
+7.5 is 11-6
+7 is 12-5
+6.5 is 13-9

So the trend has turned around in recent years, although I wouldn't want to rely on that for my bets.

One trend I'd trust is backing home dogs lined at +8 and higher.
From 1985 to 1999 they are 86-60
From 2000-2003 are 18-9.

Dogs lined from EV to +3 have also performed very well historically.