I found out yesterday, from a RadioShack owner, that the voltage is the maximum that the capacitor can handle. For example, I am using a 1 uf 250 volt cap. My nesp only uses 50 volts, so the 250 will work. If my nesp needed 251 volts, it would not. So, yes, your 63 volt cap will work.
I am almost finished with my portable!!! The only thing I need is tact switches, white LEDs and a case, all of which I am, ordering from Ben. With any luck, I can have it done very soon!!!

Life is a lot like a video game without the extra lives and continues.