I went ahead and bought a 608C and had it put on the 2188 with the condition that if it doesn't work the John Deere dealer would take it back no questions asked which they agreed to do. They claim the shaft speed of the feeder house is similar to what Deere has. The head is mounted on the combine and the Head Sight adapter are on and that all works. We will not be doing any corn for about a month due to late spring planting and below normal temperatures during the summer. We normally run 2.5 to 3MPH when chopping stalks so we will see how it all works when we take it to the field next month.