Narrow Frame + Mammoth Rider

[RainyDayNinja]

Narrow Frame:

You do not take penalties on your attack rolls
or to your AC for squeezing through a narrow space that
is at least half as wide as your normal space, though each
move into or through a narrow space still counts as if it
were 2 squares.

While browsing the Animal Archive, I saw this feat. I'm working on a character who will eventually become a Mammoth Rider, with a Huge-sized mount (15 feet wide). Does that mean the feat would apply when squeezing through a space at least 7 feet wide (half of 15, rounded down), or 5 feet wide (half of 3 map squares, rounded down to one 5-foot square)?

[Eryda]

As a GM, I would rule that you'll have to have at least 2 squares worth of space. Because half of 15 is 7, which is part thereof a 2nd square.

[Heaggles]

I would say 2 squares would still be needed.

[MurphysParadox]

Normal space is 15, half that is 7.5. Five feet is not "at least half as wide as your normal space", so you'd have to bump up to 10 feet (two squares, like everyone else says).