The rear end from the SP looks identical to the first PK Corally except the stick pack battery is replaced by the saddle pack battery. But still the chassis is completely different and the front wheel suspension of this model is a forerunner of the SP2.
I know from a reliable source that only 60 SP chassis have been made. My collection contains 2 of these chassis, 1 of them is brand new. This chassis was shown at various trade fairs.