Hi Colin,
Pleased to hear that you have your jig. I have the standard set of rods that came with the jig. Then I have two more sets. One is about 21" long and the other 36" long. These have been long enough for all I have wanted to do.
I would suggest using the shortest rods appropriate to the work you are doing - if they are unnecessarily long, then they could become unwieldly and heavy when drilling into the end of a board. I would say work out what jobs you think you will be doing and then make up two or three sets of rods of various lengths.
By the way, I have a spare G-cramp for the jig, but it has the plastic swivel foot missing. You are welcome to it if it would help you. You could probably get a plastic swivel foot easily enough. If you would like it just PM me your address and I will send it to you.
All the best
Paul