I've used as thin as .100 on smaller frame locks with .093 blades and 2-1/2"-2-3/4" blade length,but normally .125 is as thin as you want to go on a medium sized knife.
Stan
6V4 ti is very strong stuff when compared to steel at liner lock thickness. .100 is perfect for your 1/8" blade and smaller. I usually use .125 for a beefier frame lock and with a thick blade (.1875) it is a somewhat thick knife for the pocket. The thick stuff, .150"+ is cool too, but I like to sculpt it when I do a folder that thick. Otherwise it is too chunky for my liking.