Given your scenario, you have 18 points of middle value - i.e., Seattle covering by 16 and Clippers getting 2 for second half -- obviously the more middle value the better opportunity to cash both ways..
If I felt that there was no chance of the Clippers getting back in the game, I wouldn't make a half-time play -- why risk part of a sure winner.
On the other hand, if I felt the Clippers just came out ice cold and could easily make a run to get back in the game, I would likely take the Clippers on the 2nd as a part hedge, part middle.
Last year I had LSU +4 against Florida in the SEC Conference tourney and they just exploded in the first half and were leading by 13 or so..Florida came out as a 4 or 5 point favorite for the second half, giving me a 12 point middle and the opportunity to hedge against a Florida comeback -- I hammered Florida for about 30% of my original bet and caught the middle for a big winner...
Its all about value of the middle and your perception of how the 2nd half will go (maybe that is stating the obvious) -- but god I love it when given those opportunities.