where should the center of gravity be around on a deep V mono</p>

Somewhere between 29% and 35% of total length of hull,measured from the transom.
Brod..

thx brod.. u have been a big help and have given me alot of usefull info

If your asking about CG you should also take care of your strut angle.. This plays a big parts as well. And if you have trims than it gets even more sensative.
For a deep mono you should start out with the drive strut being parallel to the hull.
Then I would suggest you start to move the CG around to create a stable boat .
Start at 30% of the distance from the transom.
Moppie.

30-33% is a great place to run COG on a mono..
less than 30 will be lose but fast and fun, more than 33% and things get wet and slower..

Like Srt10 Said, Depending on what you want the boat to perform like is where you want the COG to be. Our team has a small electric boat with the COG at around 25% and it is very good fun to use. Always keeps you alert.
Tom