Using 1.3xVstall is not very handy in a Cessna as the stall speed will be so low that you end up creeping towards the threshold with barely any margin in case of gusts. It can be done, but expect to end up at the low (unreliable) end of the ASI. In my experience using 65kt with flaps 30 works on the various 172s that I've flown, with the odd adjustment to 70 in case of severe gusts. For a student I would use this as a basis and brief them on the possibility of adjusting this speed based on loading.
These are threshold speeds of course, touchdown will be at a lower speed but I cannot give you a reliable figure for that, seeing how many different variations you can get in the flare. Your eyes (or those of the student) should be elsewhere at that point anyway.
Last edited by Jhieminga; 11th Oct 2017 at 12:38.
Reason: added a bit...