what u say is bang on .. first time experimenting with tiger installation did result in complete data loss .. but that was like 6 months ago.. have managed to expand the data back to some 100gb in that time.. would not want to loose it again for sure..
and yes the partition is primary as it should be..

about installing in two diff HD ... i am waiting for the rev2 of the zephyroth dvd (have failed to successfully inject the Medevil NForceATA.kext)
with the rev2 will install leopard in the SATA HD