I recently purcahsed a set of Markins TS-327 titanium spikes to fit my Gitzo 1325 tripod. The only trouble was they came completely devoid of instructions on how to fit. The rubber pad which the 1325 has by default seemd absolutely impossible to remove. Various options on how to get the foot off seem to have been floated round t'interweb for some time, and most seemed to involve some kind of heavy engineering - hacksaw to the leg or drilling the old rubber foot off. This isn't something I felt comfortable with. FYI the feet feel really firmly fixed on to the end of the carbon fibre tube.
So I decided to see what would happen if I heated the leg up (theory: most glue melts) , so I searched for an appropriate heat source in the house. The gas hob seemed to be the best item for the job, and after a few seconds heating the very end of the leg, it was possible to grab the foot with a pair of pliers and twist it free. I'm now researching the best adhesive to attach the new spike to the tubes with.