No need to guess. Go the the EAA site and search out Neal Wilford's landing gear design spreadsheet. Does tapered rod or flat spring gear, in great detail, simple to use. I think it is in the Sport Aviation magazine article downloads section.
Thanks, I had a look at the spreadsheet. It suggests roughly 2.5 to 3" of deflection at rest with maybe 7" for reserve deflection. Good enough for my purposes. Anyone that's had the airplane on jacks lately might have an impression if that?s in the ballpark.