Recode to Sony PSP issues.

Well so far this has been hands down the all around best 2-step process to put a DVD on the PSP by far. But i recently hit a hiccup that i'm getting frustrated with. I rip the DVD to an IFO file with DVD Decrypter. Then use Nero Recode2 to burn it directly to the PSP. I've been doing it at 220mb and the quality has been so-so...it's legible but still really choppy and pixelated. So I bumped it up to 300mb and have run into an issue. No matter what i do (even locking the ratio) the file always goes way over the "fit to target" size of 300mb and in some cases goes up over 600mb!

Is there a reason for this or is there a way to insure the file will stay at the size i've selected. is there some type of overrun type deal that makes a file bigger? (i.e. should i make the file smaller so that it then overruns to 300mb?)