A Quick Question About the Combline Filter Design

I am totally new of designing a filter. anyway, I am designing a 5Ghz, 3 order chevbyshev combline filter using CST, and now Im doing a initial design of finding External Q between the 'Port 1' and the frist post (resonator) (as I think that the External Q of the two ports are the same, I guess...).

The value I calculated for External Q is 17.032, and in order to obtain a best trade-off, I made the adjustment for every elements in the filter many many times... and finally I get few values, such as:

Option 1: f=4.765Ghz; external Q=17.01 ( frequency is lower than 5Ghz, but Q is about right)

Option 2: f=4.911Ghz; external Q=18.88

I think these two is the nearest value I can get...

Could anyone tell me which one is normally used? Thanks a lot