The schematic will look a lot like( nearly the same as ) Merlin, but with some component value adjustments. Probably require a 2 sq foot top plate to do comfortably and w/o crowding.The front end is the big trouble with that design, it requires two CCS per channel. They are not too difficult. one uses the TO92 cased LND150 and can be built on ~2 cm^2 with two resistors and two mosfets.
regards,
Douglas