Encode MPEG-4 to DVD Format Without Doubling File Size
Well, the short answer is, you can't. 

The longer answer: DVD uses MPEG2 compression, which is a lot less efficient than MPEG4 (aka h.264). In other words it can't get the same quality from the same file size as MPEG4 does. 

So you can choose: similar file size, or similar quality, but not both.