I have seen references to the S5 designation. Can someone provide a definition?
The S1 had both DeDion and live axles. The axles, suspensions and engines came and went, but the basic form of a Lotus 7 has been maintained, metric, imperial, Caged, Arch, Uniroyal or otherwise.
Perhaps a series sub designation is necessary when a percentage of changes result in obvious external appearance changes to the basic form.
For example, the S2 replaces metal wings and nose with fiberglass. The S3, a wider track, updated instruments panel and roll bar. For Caterham that would include a taller and longer bonnet.
S4, we know what that was.
Back to S3, there is an S5 derivative. CSR? That would qualify.