Ok I have been trying to research this,

from what I can gather, the HD20 will not work on a stock, standard 128k mac?

From what I have managed to find googling online, the Tecmar 10mb drive would,

the profile hard drive was never used on the 128k? or the 512k for that matter

Has anyone done a CF type card project for the 128k?

What other external hard drive options existed for the 128k, in standard 64k ROM form?

thanks