i know that this is a late comment to the post but here is my take.
i have a GEO METRO XFI and when my timing belt broke on .the freeway
i was driving "65" mph (no need to incriminate my self) i had no problems with the valves touching the pistons. there was no harm done to the motor and yes its is 1.0 L ( XFI )
i know that there are some differances with the 3 different ones and i know that the gear ratios are not the same and the cam is not the same.
i was under the impressions that the XFi was the better of the bunch and i thought it was geard more for the hwy use rather than city since it got better MPG's .
the one i have now has lots of power (for a 3 cylinder) compared to some of the ones i have driven. i know of 2 other ones that are lacking in power compared to the one i have dont know what is wrong with them.
well thank you for you time
i hope i was not ranting.