yes I know it would be better for driving .....but I am afraidr that the GRP ( Midas mini) will wear out very quickly .
For the very reason that it is GRP I would suggest going solid.
Looking at the Mini, Rubber vs Solid Mount, for one thing I see in these pages, the bodies that run Rubber Mounted Frames are prone to cracking of the Toe Board, where as in my own experience with Solid Mounted Frames, this is unheard of.
With a Solid Frame Mount, the Body and Frame as as one. Any loading of the Frame is much more equally distributed in to the body, over all the frame mounting points.
In regards to Rubber Mounting, as the Frame can move, it can spot load the Mounting Points in the Body. Some Points can cope with this and some cannot. This is why the Toe Boards in Minis crack and it's easy to see why as the Toe Board where it meets the floor is a fairly strong, but inflexible part of the Body, where as the Mounts to the Front Apron are to a fairly flexible part of the body. Also, as the Rubber deteriorate, some Mounting Points will continue to work and other will become lazy, putting more local stress in to those that are working.