Any thoughts would be appreciated,
The higher you mount it the less cooking fumes it is going to be able to capture possibly rendering it almost useless. Make sure you read the installation instruction and do not exceed the recommended distances.
The Appliance Information Site
When you state the exhaust hole that's currently there, it appears your old hood ran its exhaust out through the wall instead of up through the cabinet. Hopefully, your microhood can be adjusted for either exhaust method. However - the exhaust hole going out through the wall will have to match up exactly with the microhood's exhaust vent - it'll be mounted right up against the wall. It's not like a clothes dryer where you can run flexible exhaust vent hose and bend it to match your setup. So, you'll be limited in how high you can go if you use the existing exhaust hole.
As Dan O said - the installation instructions specify minimum and maximum mounting heights. If you don't follow those, you'll run into problems down the road on everything from safety concerns to warranty work on the unit. Good luck - regards! Jim D/Heathsville, VA
[This message has been edited by Jim D (edited May 08, 2003).]