Hi Andy,
What cable are you using? I take it you mean because of the width of the GPS dongle on the top row?
There should still be room to plug a standard USB cable such as the recommended FTDI one into the spare slot next to the 1090 SDR Dongle on the bottom row. Alternatively you could put the GPS on a short USB extender - or use a GPS Mouse.
Hope this helps.
Regards
Peter