It is imperative the clutch drive straps are set at the correct height. Many get this wrong and end up with a slipping flywheel and clutch for some seemingly unfathomable reason. If the flywheel or pressure plate has been machined, the following should be carried out:

Place the pressure plate horns upper-most on something to hold it off of the work surface Place the clutch plate in position, with the protruding primary gear spline boss on the underside facing the work surface. Place the flywheel in position.

If the drive straps are holding the flywheel up, or are under tension pressing on the pressure plate horns, more spacer-washers/shims are needed between the drive straps and flywheel the movie. If there's a gap between the drive straps and pressure plate horns, the spacing between the straps and flywheel needs reducing. If no drive straps are fitted, using a straight edge or drive strap fitted to one of the horns, measure the existing gap between flywheel surface and underside of straight edge/strap, and make suitable spacers to this measurement.

The idea is set the straps so that when in as assembled position, they are not under tension, nor are well clear of the pressure plate horns. They should be just touching. Under tension the clutch will slip due to decreased clamping pressure. Too far clear may cause disengagement problems.

Marking the timing marks on the outer edge of the flywheel adjacent to the original marks prior to machining will allow them to be re-marked afterwards. And if you are very friendly with the engineering company, material is removable from the clutch plate side too. Check out the diagram for details. But, these are only suitable up to fast road use. High rpm use, even if only occasional, can see them shatter. Even more weight-saving can be achieved by the fitment of the automatic Mini ring gear as this is much thinner than the standard manual one. Therefore it should be lighter, most importantly where it counts on the outside diameter. This will also allow the ring gear register to be machined down to the thickness of the thin ring gear.