Thank you for your comments. I am actually going to experiment with both the Langstroth and the Kenya type top bar hives this year. My main objective is to transition to small cell and natural cell with about fifty hives while keeping a few conventional colonies for pollination. The reason I am going to start out with frames is to allow me to move my bees from their existing frames with their wax contaminated by years of treatments on to their own untreated comb. By sloping the sides of the frames I hope to be able to move the bees and brood to the new hive configuration and put the old comb above an older unregressed hive to be cleaned before I remove the old wax. Then I can clean the frames and let them build new comb. MB and others have suggested elswhere in this thread that the sloped sides make it easier to remove the frames without damageing them. The complete four sided frames will only be used for the transitional phase.
I will probably only use one or two of these in each hive between the standard Langstroths and the true top bars and by the time the main honey flow is over I expect to have all the colonies moved to more permenant TB hives and the original frames ready to use the next year.
I'm playing with the idea of making the transitional frames in such a way that they are in contact all the way around thus eliminating the need for an insert. I think if I can get the bees to limit their comb to these frames and move the frames so they are always in the middle of the brood chamber, the bees should keep the rest of their comb shaped in such a way that it will fit when I move the colony into a KTBH. If not, there is always the option of a knife or pair of scissors. Since none of my bees are regressed, I am hoping that using small cell starter strips will get them started with building smaller cells a little faster than the other options. It's too bad that the window for very active cell building is so short, and my age and health doesn't promise to give me too many years to accomplish this changeover, so my scheme is designed to try to cut about a year off the total regression. There used to be an old Farside cartoon with a dog working it's way through a forest and the caption "So many trees and so little time."