Thanks to the few of you who posted suggestions. I was afraid there
might be some people warning me off of higher temperatures, but I wasn't
prepared for the mass of posts.

Thanks to the person who posted the link at http://www.rhtubs.com/104f.htm
While it doesn't give any advice about hacking the thermostat, it does
confirm that I'm not totally crazy to want the temperature hotter. And
I don't think I'm in the running for a Darwin award or likely to be put
on trial for murdering my wife. If we get too hot, we get out for a
while or turn the temp down.

From the first paragraph on that web site: "Even today, in Japan, many
public bath houses have water up to 115 ºF"

As it is now, my wife takes tubs at least 3 times a week in our indoor
jacuzzi tub (wich won't comfortably seat two) with initial water
temperatures at about 112 - measured with a thermometer. So, setting
the temp above 104 would not be anything new.

We're looking for a smaller sized hot tub - and with the amount that my
wife likes to get in the tub, it might be more energy efficient to keep
a well insulated hot tub warm than to be continually heating up the 45
ºF well water at ~40 gallons a pop.

If anyone else would like to post their advice on the easiest or most
effective way to get around the 104 degree cap, please do so.

Thanks.

-JJ