Mike T wrote:

The Incline 160 did not float me in powder either, but the Wide 161 floats
me very well. The two boards have the same sidecut and stiffness... only
different in width, nose length, tail length. That extra width seems to
make all the difference for flotation!

(Warning: procede with caution - unproven theory below!)

I'll try to understand that. For a *first* approximation I think that
lift (and therefore the rider weight that can be floated) will be
proportional to board area. So relative to the 160 incline we have
Board Flotation index
160 incline 1
156 wide 1.05
161 wide 1.08
165 wide 1.11

So Mike's right, the effect of increased width on flotation is
significant - nearly 8% more for a 161W compared to a 160

Next lets try a relative flotation factor for each rider on his board
benchmarked from Roberts weight (flotation index divided by rider weight
index) :
Rider Weight index Board Flotability
Robert 1 160 1
Iain 1.18 165W .94
Mike 1.24 161W .87

Conclusions:
* Mike has least flotation relative to his weight but is probably
travelling fast!
* I think 160 should float Robert
* Robert moving to a 156W gains 5% more flotation and reduces stiffness
by 4.2 to 3.4 (but still a lot stiffer than the Pheonix). But other than
in powder, the extra width will be a disadvantage with US 9.5 boots

Iain