I just ordered the spring kit. It may be a while before I get it. Here's part of the email from Futaba support:
"Due to the very high increase in demand for these "conversion kits" for radio sticks, we can no longer send these out at no charge.
You can order a "package" through us to convert your transmitter, but there is now a charge for this.
You will need part number:
HSP00501 GIMBAL CENTER SET B $ 2.99
However, some of the parts are on back order and we do not have tentative arrival date. It could be a couple months until we have them.
Any prices provided are Manufacturers Suggested Retail Pricing only. You can order that through us at 217-398-8970 option 2. There is a $2.99 shipping and handling charge. Or, you can order it through a local hobby store and not pay shipping. They will have to call their sales rep at Great Planes Distributing and order it over the phone."