Generally, it's recommended that the bottom of the hood be 30" above the cooktop. You can go as high as 36" but lower is better.

OMGosh we had such a problem with this issue...thought I was crazy. We went from OTR cheapy hood in old kitchen to 42" best by broad island hood...well, we have 8' ceilings, and the BBB hood could not be mounted higher than 25" over the range!! Ugh-- I am 5'8", and this was way too low and I wanted to cry at how much I spent and that it could not be returned...so my husband and his dad jerry-rigged, yes jerry-rigged a $3000 hood by cutting the inside steel piece and the outer SS had to be cut too, so it's now 30" over the range. It works fine still, but we were lied to by the appliance dealer, and now I have a hood that sin't perfect-looking which makes me nuts when I think about it but the alternative was just buying a new one. DO YOUR HW! Ask specifically about the max/min mounting heights. Very few companies make hood accomodating to taller people, but since you have 11' celings you should not have any problems, in fact you'll likely need the extension duct coverings. If I could do it all over again, I would seriously consider a downdraft, or a wall-location for the range and hood. It is clear form my research that the wall-mounted hood can be mounted FAR higher than the island locations. I guess the smoke bounces off the wall and goes up so the hood is efficient at a higher point. Anyway, good luck!