I consider it less than 5%.
You believe, you consider, you think. Unless you have any evidence, this is just conspiracy theory.
I have no reason to think mtgox is not keeping 100% of their funds. As my evidence there are many mtgox wallets handling hundreds of thousands bitcoins, so there's no reason for me to think they *don't* manage 100% funds.
And bring us any evidence or stop this crap. I'm not related with Mtgox in any way, however I'm very sensitive to this kind of affairs because me any my pool is frequently target of similar accusations and I know how idiotic those conspiracy theories usually are.