Channel balance question only the research team can answer

I need to buy some S370 channel balances. The lengths listed go from 26" to 27". The balance I need is 26 1/2". The stamp on the balance is 2630. Can I use the 26" or 27"? If not, what is the cost of having a custom size made and what is the lead time? The balances I have measure 26 1/2". So, do you still think the 27" will fit? On some of the other inquiries I read, there were suggestions to use a custom made balance at 26 1/2" long. If I can use the 27", then that is great.
Scott