Hi Ariana,
I believe it should be fine, however, you'll want to submit a ticket to us on the Certificates desk here:
https://desk.lunarpages.com/newticket.php (select SSL from the dropdown)
In that ticket, include all technical specifications required for Google Checkout. We can install single root certificates for you if you need. the Chained vs Single Root is just a matter of one particular file that is appended, so the actual certificate should be fine, however, getting all specifications would be the deciding factor

I hope this helps.