George,
I have LHD and assuming your speedo is also inboard. In other words, RPM far right, centre gauge and the speedo to the left.
Removing the RH panel above your R knee, will give you access to the RPM gauge. With that removed and through the hole, you can reach the centre instrument(oil press, temp etc) loosen it and pull towards the steering, do not remove and take care not to damage the wiring to the temp gauge. Now through the RPM hole, you will be able to reach the speedo. Removing the steering will help alot and do not remove the centre instrument, only loosen and pull towards you.
You only need one elbow but an extra wrist and small hands will definitely help.
Regards
Chris