continued...
I've been doing some experimenting and found that it is unproblematic to keep also the sync, systohc, and chvt commands in the suspend file. Suspend/resume is a bit slower (but maybe less risk for corrupting anything?)
Here's my etc/acpi/suspend file at the moment:
#!/bin/bash
# switch to virtual terminal 1 to avoid graphics
# corruption in X
chvt 1
# set hardware clock
/sbin/hwclock --systohc
# write all unwritten data (just in case)
sync
# suspend
echo -n mem > /sys/power/state
# resume
/sbin/hwclock --hctosys
chvt 2