Sir....FIT IS KING
If it fits you have the basic building block.
You can add weight to the front or reduce weight at the rear......or a bit of both
But dropping an essentially sound rifle when you are able to tweak the balance point is a bit short sighted in my honest opinion.
As for an HW100 sporter being balanced !!!!!! Not my experience with the steel cylinder.
The othe point is that a heavier gun if balanced correctly will feel lighter than a lighter one badly balanced.
Having said that I am the exact opposite to you and I hate heavy and nose heavy rifles that why my 100 has lost its steel for alloy and the barrel band has gone walkies. An adjustable butt and cheekpeice make this sound gun a glove.
I would really steer you to fit and just put a little plastic bag on the front you can put coins in until you find the front weight you need on a gun that fits your body