Horn Antenna to coax pin feed

Hi. I've designed a waveguide to coax adaptor for an S band feed horn. The thing is when I was designing the conductor that goes into the waveguide I didn't check available product length and took Pasternack's PE4099(Candlestick SMA connector) as base for conductor and ptfe dimensions . Now I see PE4099 has a conductor length of 17.9 mm. I need to use a pin that is 26.47mm long (lambda/4). What should i use for pin feed for this S band Horn, is it ok to use rg402 coax soldered to SMA 4 hole flange ?.

Thanks