What Was the Score for Q-ships vs. U-boats?

I keep discovering questions I never thought about asking about the war.  I stumbled across on a BBC webpage that had the answer to a question I should have raised long ago.  Just how did Q-boats match-up against their targets.

Q-19, HMS Privet

The Q-ships, recall, were an improvised response to the U-boat threat that had the potential of starving Britain out of the war. They were designed to mimic the look of merchantmen to attract submarine attacks.  U-boats, despite what you see in the movies, preferred surface attacks in the First World War.  When the submarine approached, the ships guns were unmasked and the crews opened fire.  The Q-ship's best hope, of course, was to get in the first shot before the U-boat's deck gun found its target or torpedoes were launched.  The Q-ship, alas, was something of a sitting duck by this time.

Now here's what the final scorecard looked liked according to the BBC:

• Total Q-ships in service, 1914–1918:  193
• U-boat vs. Q-ship duels:  70
• U-boats destroyed:  15
• Q-ships sunk:  44

A few interesting notes:

One Q-ship VC was awarded to Captain Harold Auten, whose ship was sunk in an engagement in Bigbury Bay.

Q-7, HMS Penhurst

The most successful Q-ship, the HMS Penshurst (photo above), is credited with sinking two U-boats. Details are available for one attack. On 14 January 1917 she was attacked by UB-37.  After the usual "abandon ship" tactics, the Penhurst awaited developments.  The enemy closed within 700 yards and began firing.  Though hit, the Penhurst replied effectively with the first shell from her 12-pounder striking the base of UB-37's conning tower.  Other shells found their mark and the submarine sank.