FCP Export size options?

I am far from being a noob regarding FCP and compression.... but I am wondering what do you more experienced guys use when exporting HD video for the web?

The reason I am asking is normally I am exporting at either 1920 x 1080, or lower, but still high HD resolutions such as 1280x720 (16:9 of course). Now although I have messed around with much smaller size video aspect ratios, I used to know this math formula that seemed to work for converting basically any standard "HD" video size, into whatever smaller little clip size you needed to work with.

The school I am applying to needs a media submission/demo reel uploaded online to their special little page, but of course has a 100mb limit... which with the mb/sec most HD video takes up these days, is a retarded compression challenge.

Before I go through all this exporting mess - where as I could probably settle for 1280x720 but sacrifice a TON of quality, but I would rather have a smaller-visible viewing area of my video, and have higher quality.... I just want to be able to retain the same aspect/High def ratio. (I know it really isn't high definition at those small sizes but u know what im saying)

640x360? Perhaps?

Looking to figure this out again, I had a couple lower sizes that worked real well before but have completely forgot them, as I have been focusing on other things in the past year.

Thanks.

 

it's about 6 minutes.

And I didn't pluck that resolution out of thin air. I got it through a formula a while back...but it turns out the school has a requirement upload size of 640x480.... oh well.