I wish I knew the Serbian language because this video was quite interesting. The design was really elegant, the only place I could see for improvement was to make the three center blocks adjustable so that it could fit any keel. Nice job.
With small adjustments, the tool can be used for different keels.
should be in the central part of the plate to make a channel by which blocks can walk. Trough the channel is a slot through which the block is attached to the bottom side in the required position.