Synchronous cyclic sleep using Digimesh Router and End Devices

In synchronous cyclic sleep mode SM=8, using Digimesh I want Router and End devices to be asleep for 450msec and awake for 50msec. Is this possible as I worked out the (Sync Message Propagation Time) SMPT is approx 1500 msec. My number of network hops is 7. Can I lower this to make SMPT closer to 500msec?
Or do I need to worry?

No, not for the total number of hops you require.