Boslandew
I hope others will allow us a certain degree of leeway here; it would be wrong to suggest that military Chinooks do not exceed 140 kts IAS, I am sure they often do. You would have to get a Mk2 crewmember to give you the exact Vne - as outlined in the current aircrew manual/ODM. The Vne would be approx 20 kts higher, but do not quote me.
The Puma could rarely manage 150 kts IAS straight and level (s&l), most Vmax computations were between 130 -140 kts IAS for a given Mass/DA, but as the ‘ol girl’ gets heavier I’m sure she would struggle today to exceed >140kts IAS s&l – certainly would make your teeth rattle.
The 120 kts is a good planning speed, which, I’m sure you appreciate, gives you a degree of flexibility to increase your speed if you have a Time on Target to meet.
P.S. Your question was actually about cloudbase limits when operating >140 kts - same reply, not aware of these limits being stated etc.