Cisco 3750 Stack standby switch

I have been working to configure a stack of 3 WS-C3750X-48T-L  so 2 members are active and 1 is in hot standby mode. From the best I can understand reading and rereading the manuals standby switches that would roll in to take the place of a failed switch isn't possible with stacks.

It appears to make this work you must use switch clustering HSRP groups. I am confused about clustering and cluster command switches. Can one of the active 3750's act as a command switch. If so then can a cluster of 3 be configured so 2 are active and upon a failure the standby takes the configuration of the failed switch?

Essentially you have two choices based  on what you're looking for. For the automatic configuration of a replacement stack member, you would actually need to leave your stacks at 2 switches. The automatic reconfiguration comes when a switch fails, and you physically remove and replace it with another switch. The new switch will detect that another switch is already running in the master role and will accept the existing configuration.

Your other choice is to have a stack of 3, with one of the switches running empty. Upon a failure, use the current running configuration to copy, replace interface numbering, and paste in to place. Then move the cables.

There is no way to have a stack member automatically take on the config of a failed member... At least none that I know of. The better answer to this is to get your customers to do, well, what they currently aren't doing which is dual connecting their equipment.

(Caveat to my opinions - I've never done clustering myself, we've always used either stacks, 6500's in pairs, redundant SUPs, or other means of providing HA capabilities)

I don't believe that clustering would solve your problem from my reading of Cisco's docs...    The two WS-C3750X-24P-S switch cluster that rauenpc suggests looks like your best bet.  If you're really worried about swap out time, you could rack three switches in and simply leave one disconnected.  The amount of time it takes to replug the network cables and stack cables shouldn't be that significant especially if you leave the middle of the three as the cold standby unit that way you'll only ever remove the top or the bottom switch rather than pulling out the middle switch (if your top switch dies and the bottom of the three is the standby, your re-cabling gets messy real quickly). 

Honestly, I have to agree with rauenpc's recommendation on driving your customers to "do the right thing".  And, unless your SLAs are written to require this kind of failover, you're probably costing yourself more money trying to compensate for a customer trying to do it on the cheap.