Well, for this plane it is important to have as many as you can weight in front of CG. My plane came with about 8 kg. Mostly Because it will be powered by Zenoa 26 (1.8kg) and retracts are big ones, for planes with max weight 15kg.
Glasing, panel lines, rivets and painting has added 0.4 kg.

As I can see manufacturers are making retracts in categories 5-8kg and next is 8-12or 15. I thought that putting it on maximum load is critical. With this setup I hope that I will not need any lead in front.
I have Robart tail wheel but did not manage tu put it inside. It is lite but not strong enough for this weight.

Of course we want to see all documentation that you have. Please post it. Or we have to vote?