Posted 2016-January-18, 15:42
In principle I believe you should not be obligated to cuebid 4♠ - this has nothing to do with it being only a second round control though, if you play mixed cuebids at the 4-level (as almost everyone does nowadays) you should do it throughout and not try to think of exceptions. The important question is inhowfar partner has shown slam interest with 4♣, i.e. which hands would he bid 5♣ on instead. If 4♣ shows slam interest, your hand is quite suitable and you should keep cuebidding. On the other hand, if 4♣ could be "I'm just keeping the bidding low out of courtesy" (or, worse yet, nonforcing), well you are somewhat minimal for your 2♣ opening and you have probably done quite enough by cuebidding 4♦.
I like to play that 4♣ does show some extras (say 6+ and not just queens and jacks) so I would cuebid 4♠ here.
"One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision"
-- Bertrand Russell