There is a new Chrome app available for your Chromebook which may solve your problem. Note: It will print over your
LAN (much quicker than
GCP) although you cannot use it for printing from a remote location via the internet (something you can do with GCP).
If you install
HP Print for Chrome from the Chrome Web Store, then initiate
Print then change the destination to your HP 5530 (which should be listed in
Local Destinations if it is switched on) then click on
More Settings you will see a
Paper Size multiple choice selection button.
In my case I can select a whole range of paper sizes for my HP Officejet Pro 8600 including 6X4 and 7X5 inches.
Is this the beginning of the end for GCP?