As you'll see from the chlorine post for spas that Jason linked to, there are some differences than using chlorine in a pool. The bather load is much higher since the water volume is so low in a spa and they are typically covered so most of the chlorine loss comes from bather load, not from loss from sunlight. The other big difference is the amount of aeration in the spa, especially if you use jets. Getting the TA lower (to 50 ppm, if needed) and using 50 ppm Borates in the spa are important, even though the procedure says that the borates are optional, I'd say they are normally required to keep pH from climbing too high too fast even with the lower TA level.
