You probably have already done this but here goes.

I located my battery and reciever under the fuel tank, that helped.

I am powered with a .52 4 cycle which is the same or lighter than a .46, so I added a one ounce spinner nut on the prop shaft rather than a spinner.

Just to be sure, I epoxied 2 ounces of weight up by the engine and when I hold the wing tips, (actually 2 of us) at the main spar the bird just tilts it's nose gently forward.

If you have to, 4.5 ounces is not a lot of weight and the bird won't notice it too much.

VR Mike