I have been trying unsuccessfully to get the google checkout module to use my zencart shipping estimations...and I am at my wits end. So trying to think of a way round it I came to the conclusion that perhaps this might be possible...what do you guys think?

Would it be possible and not too hideously difficult to add another payment option, something similar to the pay buy cheque button, which would allow a customer to opt to pay by googlecheckout.
Then I could work out the cost of the shipping, add it to their order total and send them an invoice via e-mail from my google checkout account.
Does that sound like it might work?

If the above is not advisable...is it possible for someone to point me to a step by step guide to actually getting my royal mail module shipping to show up on google checkout, as at present it is showing £1.00 shipping on everything...no matter how much they order...

Otherwise I am just going to give up on google checkout (which I don't want to as I know many customers prefer it)...as it is driving me mad...