Thanks, Paul. I chose this method for myself (filling the spacing with linden) 4 models back. In Russia, many modelers use it. They are filled with either linden tree (it is cheaper, but heavier) or balsa (it is easier, but more expensive). The filling gives a good result of preparing the hull before sheathing. If everything is properly sanded, then no putty is needed. Yes, this method adds extra work, but I like the result. The body becomes monolithic, and when sheathing it is possible to insert the rail holders at any place, and not in the rib of the frame. In general, I tried to explain why I am doing this.