Dont forget guys it is an accepted & approved procedure to leave the gear down after departure for cooling if required. I have never seen any performance correction figures for this but I suppose you could use gear down (ferry) performance for the 4 segments and then you would be covered.
S&L
EDIT Sorry I missed the bit about "after an engine failure at V1?" obviously you would bin the cooling and raise the gear. No idea how quickly you are supposed to do this.
PS If it helps, we time the gear retraction at 130kts on airtests and it has to be up within 10secs (737). This obviously takes no account of how long it takes for you to remember to raise it when the heat is on!