I've actually had some success with Multiavchd. Good news, you DON'T have to reencode the video at all. When you go to the Media directory to manipulate your video files, click on the transcode button. Once you get in the transcode menu, near the bottom there's a prompt that (if I remember correctly) says something along the lines of BD or AVCHD compliant. You can click on that, which brings up several encoding options including NO RECODE or somesuch.

On a side note, I've been using Multiavchd to create custom Blu-rays with working menus. Although the menus are a bit rudimentary and the program has some annoying limitations, it beats not having any menu at all for a disk with a movie and extras. Even better, knowing what files to edit, you can also label the disk and create a thumbnail icon for PS3 (requires some extra steps outside of using the program).