11 HCPs - open or not?

Flatish but the values are in the long suits, a good rebid 1♦ -2♦ and it meets the rule of 20 (Here is Andrew Robson on it). So open 1♦ 

East has a choice of overcalling 1♠  or as a balanced 5332 . 1♠ shows 5+♠ s but has a wide range 7-17 (with stronger hand double first). The advantage of 1N is that it shows a specific balanced hand with 15-18 HCPs. Here is Andrew Robson (again)  on 1NT overcalls

South with a good hand and a 6 card ♥ suit will bid 2♥ 

North with a minimum opening hand with the strong hand on the wrong side (downgrading the value of some of the HCPs) should pass.

East has shown his hand once and is Vulnerable will pass as will the others.