You cannot take the 1394 ELO. Because otherwise you will have to increase every computer in the Info Active list accordingly. You have to deduct 200 ELO from that. Active ELO is 1179 is really about the best you can do. Trust me I played U1400 tournaments with over 1000 games so I know these machines very well. So your logic would really not get it higher than about 1500 elo max.

ps... and they wouldn't achieve even that. They lack in many games the ability to find a plan and settle instead with draws by 3x repetition (even with a huge piece majority) and they have total inability to check mate from positions that even 1500 elo computers would find. So even 1500 ELO in true practice with speed doubling is too high.