Hi jamesp,
Don't lower the MAX bit rate. Use file prediction to find the correct CQ value. If you lower the MAX, you might see blocks on high action scenes. At MAX=5000, it's good enough for 720x480. At least with TMPEG. Why the commercial DVDs have MAX bit rates in the 8000Kpbs

Because they are crap

. The mastering being done on studios with million dollar equipment is all based on "muscle power". High bit rates with poor quality encoders. That's why even some DVDs look like crap on HDTVs. The KDVDs I've done with a MAX of 5,000Kbps at 720x480, look better than many commercial DVD players

. Oh yes they do, and that's on MY HDTV

So you can figure that with the new techniques, you can fit ~6 hours on a DVD. So divide your DVD size/3, taking into account audio. So if you want to put three movies on a DVD, your mpeg size per movie will be ~1.43GB in size

You might want to change the resolution on KDVD Full D-1 template to 704x480. That will buy you a little more space without sacrificing quality, and it's still a valid DVD resolution
--kwag