[BrianG]

Generally, using two or three smaller caps is better than one large one for heat dissipation (more surface area) and transient response. So, if you want an extra 1000uF, you can use three 330uF instead. Each cap has to be rated for at least 25% higher voltage than you plan to run. For 4s, that's a 25v cap; for 6s, that's a 35v cap; etc