Wider boats are more stable, hull separation does affect performance as well
as individual hull fineness, and overall aerodynamic drag. If a catamaran is
too wide for its length it can become diagonally unstable and pitch
excessively,however a high CG can cause the same. It's about balance. The
Manta with relatively fine hulls (11:1), light displacement (24000 lbs), good
hull separation (21 ft. beam), low CG and aerodynamic drag (no flybridge), has
excellent stability and performance (20 knot top speed with a pair of 160 hp
D3 Volvo's).

Pat,

I think we all understand that a wider boat is inherently more stable
than a narrower one, given the factors that you mentioned.  My question
is, if you added 10 feet of length to the Manta 44, keeping all else the
same (hull shape, VCG, overall beam) would it become less or more
stable?

Bob