Hi Tom ,
You are talking about how to use a RTOW chart in normal conditions. Minimum V1/Vr/V2 speeds are not just there for decoration.
There are some rare cases like: a very light aircraft in wet conditions use of engine anti ice , where speeds have to be reduced and the resulting speeds would be below minimum speeds. In that case speeds have to be compared to minimum V1/Vr/V2 speeds.
V1 can not be lower than Vmcg therefore a minimum V1 has been defined
V2 can not be lower than VMU that s the purpose of a Minimum V2 !
if V2 is below Vmu , Flex take off is not allowed .