Can value of max_subs_percent in Thin pool be increased .

I  have  a VMAX with 5875 code.

I have a thin pool of FC disks with max_subs_percent set to 100%  ..pool is  just 40%  utilized however i am not able to bind  new devs (TDEV) to this  pool hence i want to increase the  value of max_subs_percent to  value larger than 100% or None .. 

a. Can i do this in production(on the fly) without any downtime ?

b. What is the procedure to  change the value 

c. Later  on  can we  change it back to 100%  once new disks has been added to the VMAX array  and new data devs added to the pool..