Zap, I ran without guages for a while.. in the spirit of a true hotrod streetracer.. got me in trouble one day racing a Duc, could not hear my revs and overrevved a bit.
After riding a 750 a lot, you get a feel for 30mph in 3rd, and 55 ish in 5th.. if you get in a 45 or 50 zone..use 4th..
If asked to do 30 mph without clocks, I can probably get within + or - 4 mph easily.... not that hard.. The other thing you do is watch the rest of the traffic.
I rode that beast to Bonneville and back like that.. in 07