Can you please specify what year off of a 6G and 7G that you are inquiring about? For instance, Honda normally runs a generation for five years (i.e. '03-07) and normally does a face lift on the last two years of the generation (i.e. '06-07) which some times includes a different bumper, trunk lid and tail lamps. This can affect which spoiler can/will fit.
You'd have to take measurements. Even if it did fit, spoilers usually are designed to go with the body lines so they end up looking out of place on a different model. You can probably find very cheap OEM style or even OEM floating around eBay.
Based upon the following pics I would say no. The 6G has a very flat, squared off trunk lid and rear quarter panels. The 7G coupe received a much more rounded trunk lid and panels. The only way to be 100% sure would be to actually get a hold of the 6G spoiler, measure the width of the mount points, and test fit it onto your trunk lid. It may look awkward with the curvature of your 7G, though. They are very similar spoilers...just by googling 2003 Accord coupe spoiler, I came across many places selling them for your 7G for < $100 and only another $80 if you wanted it painted. Why not just go that route?