deadsea - 4:38 pm on Oct 1, 2012 (gmt 0)
The only definite 'yes' would be to redirect them all to the correct pages on the 'new' site.
It sounds like you are taking the correct approach by starting with the most important pages. But, only redirecting 17% of the urls correctly is an SEO disaster waiting to happen.
I would look for a way to automate the process. For example if there is site search available, I would write a script to plug the title of the page in to try to find the new url.