How much volume do I need for a barley wine?

I'm brewing my first Barley Wine, and I think I have enough headspace in my primaries, but I don't want to find out when the top blows off at 3 in the morning.

I'm doing 8 gallons of 11% ABV (1.101 SG)

My plan is to put 3.5 gallons in my 6 gallon carboy with a blowoff, and 4.5 in my 7.8 gallon bucket (no blowoff on this one).

I'm pitching most of the washed yeast from a 5.5% ABV Pale Ale I have sitting in my secondaries.

Any idea if I'm OK?

As long as you have a blowoff, it shouldn't matter.