Source of 3.5mm travel of SKSF switch is ALPS catalog '94 edition.
That of usual Bigfoot class ALPS is also listed as 3.5mm in that catalog.
Checked my blue clicky ALPS. My vernier caliper indicated key travel as 3.5mm. Actually the length of a stem from the upper case to the top oa stem is 4.0mm, but there still is 0.5mm left from a surface of an uppercase when a stem is pressed down completely.
Show Image
(http://www.google.com/patents?id=0M46AAAAEBAJ&pg=PA4&img=1&zoom=4&hl=en&sig=ACfU3U3oVwbj7aKmQHnqhLQAA6Oh5K4nRw&ci=155%2C277%2C808%2C750&edge=0)
It's for a plate spring switch. No relation with M1242 switch so far.