I was looking at these gearbox attachments on the Stihl website. Could I use the "FC edger" attachment on my FS90R? http://www.stihlusa.com/accessories/interchangeable.html My dealer said they had never even heard of the gearbox attachments before. I could really use an edger but don't have the money for a whole new power unit right now. If somebody could clarify if this attachment will work on my trimmer or not, I'd really appreciate it. Thanks for your time.