Question about shipping

I printed off a shipping 7 oz label for $1.97 through Paypal. The weight was based on me using a bubble mailer. After I printed the label I decided a box would be better. The box will with the cards is 8.8 oz's. Can I add a stamp to make up the difference? Or is it a no-no to to mix metered mail and a stamp?
Thank you for your help
Thank you for your help

My daughter was diagnosed with type 1 diabetes at the age of 2 (2003). My son was diagnosed with Type 1 when he was 17 on December 31, 2009. We were stunned that another child of ours had been diagnosed. Please, if you don't have a favorite charity, consider giving to the JDRF (Juvenile Diabetes Research Foundation)
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Comments
No, I do it all the time. In fact, you should buy discount stamps on ebay and save 10-15% (if you ship enough), mix with meter to get correct rates.
Clear Skies,
Mark
Raw: Tony Gonzalez (low #'d cards, and especially 1/1's) and Steve Young.