Dear Pete, I own the classic Helicopter, the curvy copter and the clover cube plus - all of which i recently got to enjoy solving on. What would be your recommendation for the next (one or two) additions down the line?
I think a good next step would be the MF8 Curvy Copter III. It is a fun curvy copter variant. The LanLan Oscar Crazy Comet is very much a curvy copter variant, even if it doesn't look like it. Something a bit harder would be the MF8 Skewby Copter Plus and something a bit easier would be the MFJS Maple Leaf Skewb.
