I have always done that - I learned very early on that if you wedge it a certain way then it will be unlikely to fall over due to the motion of the train (it's happened 3 times in about 15 years).
It never ceases to amaze me just how many people I see who never realise this and have their bikes either blocking another area (such as the seats), or they just stand glakitly beside their bike for the entire journey not realising. I ued to try and explain to people, but they obviously were too dense to realise what I was saying.
I go and sit down near to the bike and only get up to change what side it is on depending on the next station (or on the VERY rare occasions I hear a 'Crash'
). If they want to stand like an idiot, let them - more seats for the rest of us.