The IMPBA F hydro oval speed record is 72mph. That boat was doing 99mph at the end of the straights.
The 20 record is 63. I think that boat was running about 75 at the end of the straight. I am sure Andy or John knows the speed.
If I remember correctly, if you are 5 feet from the inside guy then you will have to be 5mph faster than him just to stay even. This is consideering a constant speed of course. Now if you quit being so concerned over speed and work on time then you have learned something. As we all know, speed is lost in the turns. A lot of speed! So how do we compensate? By building a faster boat. I can tell you now that theory is not the best. John Finch built some boats that were not the fastest down the straight but they turned like nothing else. The result was him reducing the record times by over a second in some cases. To drop a record by one second is HUGE!
I do not know where Roger's lap times went to but he was on the money with how to judge speed.