Robotron shafts... 4" or 3.5" ?

[LeedsFan]

I just got hold of three used Wico joysticks. They need a cleanup and a bit of a refurb but they are solid and complete none-the-less. Two of them are 8-ways and one is a 4-way. Now I intend to use the two 8-ways for a Robotron panel. These sticks all came with 3.5" shafts with red ball tops. In all honesty for what it costs I may as well buy NOS shafts as they are available.

My question is should I get 4" or 3.5" ?  I know the original Robotron shafts were 4" in length, but does it actually make any difference in feel to the game? I'm thinking 3.5" should be just the same no? The reason I ask is because I'm in the UK and I can get hold of both sizes here, but not in red. Any colour but red. I can get 3.5" red NOS shafts from USA but the postage and customs clearance etc. kills the deal stone dead. I'm just tired of forking out £20 - £25 extra on goods from USA.  

EDIT: crap.. I posted in wrong section sorry. Can a mod please move?