Any cricket fans...

game enough to step into the breach with a declaration both in score and timing?

I'd say a lead of 375 and declare a little after tea time. If they try to get 450 as some are suggesting, that will only happen tomorrow some way through the day, and there probably won't be enough time to bowl England out .  

 Declare  410 runs  England bat for 1.5hrs

I would do the opposite of whatever Dens e says.

 I would normally also do the opposite of what dense denise says but it worries me that I might then make the same call as ou rooitwit who so often gets it wrong Bwahahahhahahaha 

 This is past tense.   I it did not rain De Villiers would have declared at 400 - 410 - every batchman was hitting out at everything indicating a near declaration.  He did not make a complete hash of things when a few years back Graeme Smith made a fool of himself in the Melbourne test and declared with a lead of 278 runs, when the Proteas head a distinct advantage and the Aussies won the test with the greatest of ease.