If you're usually comfortable in regular economy, then C+ is probably not worth the upgrade in your case. Do you know the particular type of plane you would be flying on (in each direction)?

You wouldn't be able to do a paid upgrade from a V fare without having to get your ticket recoded/reissued, which can cost a lot of money.

How much extra is the full fare ticket? It might be worth it if it is still much less than than a business fare, but keep in mind that upgrade inventory is often much less than actual seat availability. What kind of upgrade certificate is it?