I can play the top four strings of any fiver no problem, just as I can play any four I have tried and feel right at home. But I am not considering a fiver just to get a string that I can use occasionally. If I go with five I intend to play all five, all the time. There are only five extra notes available on a fiver after all, the fifth string not the extra notes is the main draw for me. So I would say that the neck width is an issue. You want to find one that you are comfortable with. For some people this is no problem, others strongly prefer either narrow or wide, and at least a few are like me and find that the left hand prefers a narrow neck while the right hand prefers 19mm string spacing. The optimum for me seems to be Ibanez. Peavey is too narrow, Schecter is too wide (but only a little), and anything wider than a Schecter is way too wide.
BTW, if you are looking for small fivers, Guitar Center carries an ESP short scale in both four and five strings. It has a tiny body which makes it hard for me to play seated without a strap, the usual GC condition, but others have tried and liked so it is worth a look. I don't recall the model number, I don't believe it is listed on the GC website or the ESP website, but there are at least two threads here about it if you search for them.
Ken
BTW, if you are looking for small fivers, Guitar Center carries an ESP short scale in both four and five strings. It has a tiny body which makes it hard for me to play seated without a strap, the usual GC condition, but others have tried and liked so it is worth a look. I don't recall the model number, I don't believe it is listed on the GC website or the ESP website, but there are at least two threads here about it if you search for them.
Ken