Most all round engine planes had a short nose to handle the massive weight of the radial engine. Ihave had to add 9 oz on a much smaller plane. One trick to get the weight as far forward a possible is to hang it under the engine. I've use the Galvanized U shaped condut straps as a base, get them to fit the bolt pattern of the engine, the make a wood moldand position the strap so the lead will not interfer with the bottom of the engine, and will cover both sides of the strap as well as around the edge. Use long engine mounting screws and some washer and some thread lock on the nuts and they hold up quite well. Iwould use two straps and one pour of lead for that much weight.

Don