The general requirements are;  large taper, little or no twist, large chord, slow RRPM, large solidity ratio, advancing blade concept, pusher prop and an increase in horsepower that is appropriate for the desired maximum forward speed.  

Hope this helps.

Builder,

There are no easy answers to your question:
a) When the tips of the blades exceed Mach 0.85, you have a problem.  You have to do the math to find out how big your rotor can be for a given fwd velocity.
b) More power = more speed, also more power = more weight = less speed.  You have to do the math to find the best balance.
c) the faster you go, the control system evolves, to accommodate the attitude of the rotor disk (cyclic).  This is an elaborate analytical task, so my comments on this part end here.
d) Drag on the airframe is a "minor" concern in rotorcraft design - I put it in quotes because it takes a backseat to the rotor design task.  The faster the heli goes, though, the drag increases esponentially.  Computational fluid dynamics are used to optimize the config for high speed.

The equations, as you can tell, are inescapable.

STF

Gentlemen,

Thank you for your input it is much appreciated. I plan on going with the new technology of blade tip speed of 500 ft/sec, large chord, tapered with a 6* twist. Dia. of 26ft. with 525 Hp. Gross weight of 2000 lbs, would like to cruise at 180 mph ??(hopefully) Thank you again

The RoterMouse is a 600 lbs helicopter (empty)
with 145 hp turbo-shaft (jet) power plant
single seat
taper,camber/chord of 21 ft die.
cruise speed is 160 mph
Its the power/weight ratio and simple design