Some girls are comfortable with only seeing one guy at a time when doing online dating and some others are comfortable with seeing about a handful of guys when doing online dating.
It really depends on what the girl can handle and what her history in dating has been like.
So much depends on your attitude when it comes to online dating.
If you are bitter about being shorter than 5’7 and reflect that bitterness in how you go about constructing your online dating profile and how you go about chatting with people on the dating site, you will have a difficult time attracting a match.