Thanks for the prompt response.
However, because the Max speed is the same for all (319/320/321), the ROD may not be all that different.
Also, the Cabin length of a 321 is much longer than a 319. If anything the time available for keeping the cabin pressure within acceptable limits in case of 319 should be substantially more than a 321. So if a 319 is restricted to 37,000 the limit for 320/321 should be substantially lower.