balance length

Hello,I bought some used vinyl windows with non welded corners so I could disassemble them and make them smaller, about 20 5/8" wide and 36 5/8" long. They were about 28" wide by 53" long. They will be oriel style. The top sash will be about17 1/2" by 23" and the bottom sash will be about 18" by 13" with double glass 3/4" thick. The balances were 5/8" but I think I need to replace all balances. My questions are-

1. what length balances should I use
2. should the balance for the smaller sash (or both) be a thinner balance and what color tips?

Thanks in advance and if this is too complicated just delete it. Terry