Hugo I tried the Lotus on sports tires last night when I was racing and I did not like them much, the sports softs had better wear but the rears went off substantially and I doubt they'd last more than 2-3 laps longer than racing tires do depending on the track.
As far as 80s F1 none of us know what the grip was, Rubens Barrichello has said that the Lotus 79 the first ever real good F1 car drove similar to his Ferrari F2004 when he tired it.
Senna's lap in 1987 was 1:40, I did 1:33 at Suzuka in 97T maxed out on tuning, race softs. Alot of that is coming on the straightaway Hugo, as I was hitting 208 mph, the real car probably had about 195 mph. So corning speeds are comparable. The real car probably was 2-3 mph slower in the S bends at Suzuka... Also factor in the video game aspect of having zero consequences.
That's worth a couple seconds.
Another thing Hugo, are you corning and accelerating using the H pattern shifter & clutch, because I bet those paddle shifters or that fully auto gears are worth some serious time! I know I would be damn lucky to beat the Senna laps with H patter shifter.