I think you'll be asking for a LOT of honey flavor if you use that much - though clover is a mild honey, you've got about 30% of your fermentables coming from it. Also, this will be a pretty high gravity beer. On the order of 1.080.
What is your hops boil schedule? make sure you have enough bittering hops to balance the sweetness.
Don't get me wrong. I love a sweet porter. You just need to make sure its balanced. Also, I've never used dark DME, so maybe there's enough bitter character there to do the balancing?