RPVST M4250 quicker convergence

Hi,

Looking to see if anyone has any suggestions on how to increase the convergence time of RPVST? It is taking about 6-12 seconds. While the switches are rarely powered off or cables unplugged we would like to get this time reduced - in the event we do have to do some maintenance we want to limit any of our off-air time. Coming from a Cisco background I'm used to under a second convergence. I will be coming in at some point in the future to review and adjust the configuration but was hoping the community would have some more information.

What I noticed is there is a "Hold Time" of 6 seconds configurable by the "Spanning Tree Tx Hold Count".  I tried to find more information about this but can't seem to locate any. Would lowering this improve convergence? - the minimum setting possible is 1 second. 

Another question - is Netgear RPVST protocol compatible with Ciscos RPVST protocol? We have both the Netgear M4250 and Cisco 9200. 

Any other suggestions would be appreciated

Thanks