Convert MKV w/ .ass subs & effects to MP4. Sub effects won't stick. Mac.

Maybe somebody here can help me...

Short Bullet version:

• I'm running a Mac
• Made subs in Ageisub w/ fade effect
• Used various convert apps and fade effect doesn't convert to video
• Already tried HandBreak, MKV Converter, and 4 other apps.

Longer version:

I have an mkv with .ass subs that I made myself with Ageisub. The problem is when I use my go to app Handbreak to convert it into an mp4 the fade effect on the .ass subs gets dropped. Instead of fading they just disappear like regular subs. I've also tried about 5 other video converters (free & paid) from the App Store.

I know I can do fade subs/titles in iMovie, but I'd like to figure this out since I'm likely to come across other mkvs with styled subs (fades or whatever) that I haven't made (or might make) myself and would like to know a good way to convert these while keeping the effects. I'm planning on uploading the video to tumblr/youtube/whatever for others to watch it. It's just a short video.

Ideas? Suggestions? I asked in other forums and one only mentioned Windows programs despite my saying I ran a Mac. The other went on about how I don't need to convert mkvs to mp4.

Thus, I ask here.

Thanks in advance!