MX5 rear upright bush?

[TalonMotorFabrication]

Been chatting to your man Mark via email past few days about buying them in bulk as every one who has MX5 running gear is going to need these bushes at some point.
The rubber bushes on both pairs of my uprights are shot and are very soft as a result, however given the design of the Saturn top wishbone and where the coilover mounts on my TMXR design I'm thinking that a harder bush would help transfer the movement of the suspension to the coilover better. Any body that has the Saturn design on the road and using a higher spring rate got any thoughts about this?

I would seem to be the logical person to arrange a group buy and get them sent out as I'm around during the day to take deliveries and arrange courier collections.
I'm looking at keeping things very simple incase this back fires on me and only supplying them in yellow or black not that they will be seen behind the rear disks.