INFLATABLE STAND UP PADDLE BOARDS SHAPED FOR BALANCE
Stability usually comes with a wider board profile that allows the overall shape of the board to balance a rider more easily than a narrower profile. A 6" board will offer increased weight handling though if weight handling is not an issue, a 5" board is preferred as the lower profile makes it much easier to stay balanced on the SUP. The choice of an 'ultra stable' SUP should come down to what your primary use of the board will be such as all round paddling, yoga, whitewater etc and crossover between water types.
For more specific information on Ultra Stable SUP boards see our Buyers Guide article How to Choose an Ultra-Stable Inflatable SUP