Recently did IB-LA (the MAD-FRA leg) from T4 to T4S in 12 minutes.
Extremely lucky with the shuttle train being bang on time and no queues and passport control.
Pretty much out of breath but made it. Wouldn't want to miss the 787 on LA and being put on a IB A320 instead.
T4S-T4S in an hour is more than ok then, especially if on one ticket.