>increase performance. I looked inside my hulls and found that there is no horizontal bulkhead in the front part of the hull is it common in Tornados?<
Common for '1970 ish fiberglass Tornados.

>I thought that installing bulkhead would be great performance improvement, has anybody done something like this?<
That is what developed say 80's fiberglass Tornados. A subdeck and bulkheads were added and obsolesced the older boats, perhaps someone can chime in with the details?