In stock factorio, you can shift-right-click a machine and then shift-left-click a storage chest to set the storage chest's filter, and onto a requestor/buffer chest to set request slots.

This appears broken with Ultracube.

It appears to work for me, and I don't think ultracube changes anything about that system.

It works for me, sometimes the numbers gets crazy high, (like it requests 1200 basic matter unit for just a 240 recipe), but I experienced the same problem on Pyanodon. I just double check and change numbers manually if necessary.