Hi Zap, All looks very good as allways
You will have to modify that block design slightly as those channles are near impossilbe to mill even on a CNC. The best way to machine thin channles like those is with a slitting saw (like a small circular saw) but that woudent work with your design as theres no clerance for the saw at the end of the channles.
If you did them on a cnc you may be able to use a very small diameter endmill but its difficult and time consuming. The outer shape of the blocks are fine but internaly i think they need a bit of work to make them easyer to machine.