A right handed ankle holster will be for the inside of your left leg. Its a bit different at first but i have never banged my ankle gun on anything. You will be constantly looking at your ankle for about a week while wearing it though. But keep in mind no one looks at your ankles so a small bulge is not noticeable to anyone.
I would like to persuade you to consider a different back up gun though. Considering your primary gun is a glock 17 you should carry a bug in a glock 26. Same exact operation and will take the spare glock 17 mags. This is my exact setup. G17 carried IWB at 4/5 o clock and a g26 in a gaclo ankle glove. My ankle gun is a backup to me and a way i can arm someone else(family,friends,stranger) if i have the need in a active shooter situation.