This is part of my native tree challenge, but asking advice on attaining my future goals? Got these gems at my favorite local (non bonsai) native nursery here in PA. Alder no. 1 back bud like crazy after the major pruning of all pre existing branches in winter time. The tree is covered with paste to heal wounds which is healing. The top however not too sure about , and since the wood is soft I was going to plan on hollowing out eventually. First picture is tree now, next is a quick sketch of where I’d like it to go. Third is Alder no. 2 it’s a big ol clump and is back budding nicely , should I prune back to the back buds? I’m afraid if I do that the deadwood where the original leader(which died off) won’t heal. Advice ?