Sounds like you'll be taking the shocks off. Or you could borrow a neighborhood kid; "Hey kid, come here...want to help me work on my motorcycle? Take this spanner and stick your hand up underneath the fender".
Just looked at Jack Lilley's site. Speedmaster solo seat = America solo seat. Same thing.
Just thought of something to try. If you have a long 1/4" extension, put a union on the end, and then the right size socket on that, you might be able to get to those small nuts that way. Those little nuts take an 8mm socket.
