If you have the original pitch trim system as shown in the plans, you may not have enough pitch authority at those higher speeds. Like my plane, most 0320 powered Long-Ezs that I know of, carry at least 20 lbs of ballast in the nose. I finally converted to an electric pitch trim, sold by Alex Strong and that solved my trim issue. Take care of the CG issue first and make sure you stay in the "first flight envelope" as shown in the operator's manual, for the entire flight test phase.
Steve Rothert
Long-Ez N49SR