Recently did my first race.
Thought it would be fun to try out.
Instead of 3 seperate starts, at the last minute they went with one giant group start. So EVERYONE started together.
I had an infection the days before and wasn't feeling well so couldn't hang with the main group. It was I think around 10 laps, total distance 112km. I finished 2 laps down and rode a fair bit in no-mans land. Looking at the results. Several of the registered "Senior 4 Men" which I believe is our equivalent to your Cat 5 finished on the same lap as the top riders in the top division. Even if they hung on to the back of the pack for 112km, is that how close it is between the slowest group and the fastest groups?