Iād like to warn about switching hands. Iām studying Psychology, some time ago I wrote an essay about the impact that switching to your non-dominant hand can have. This may sound strange at first, but thereās some evidence that supports it. Itās a bit hard to explain shortly, unfortunately the essay I wrote is written in german so it wonāt help you that much I guess.
Your brain is lateralized, which means that one hemisphere is specialized, for example the left hemisphere usually is the ālanguage expertā (In almost all right-handed people). Damage to the left hemisphere has a high probability to impact your ability to speak. The left hemisphere usually also controls the dominant hand (nerves cross on the way down to your body).
The basic message is that if you use your non-dominant hand, you act against the anatomy of your brain, which runs your brain into trouble. To give you an idea what Iām talking about, have a look at this paper. Itās a PET-study, so the nice and easy to understand part are the brain scans. Have a look at Figure 2 to on page 2819. The participating subjects grew up in the GDR, where it was common to learn left-handed children to use their right hand for writing. You can see that ānormalā right-handed people are left-lateralized, left-handed people are right-lateralized, but converted left-handers arenāt that strongly lateralized. Some of those āconvertedā children are said to have problems with attention, memory, motor functions, and maybe this one of the reasons for dyslexia.
This still is a big maybe, and thereās a big difference to you: While you use your left hand for the mouse as adults, those children had to write with their left hand. Writing is more complicated than holding a mouse, and it hit them when they were still growing up (so in a time critical for development).
Still, take care. If you get problems with attention, memory, motor functions or something like that you maybe shouldnāt switch hands.
About RSI: I bought a dumbbell and actually used it. Some more muscles do help. Of course, also use the mouse less. Some people say that a trackball helps, but that isnāt an option for ET I think.
Siebner HR, Limmer C, Peinemann A, Drzezga A, Bloem BR, Schwaiger M, Conrad B (2002): Long-term consequences of switching handedness: a positron emission tomography study on handwriting in āconvertedā left-handers. J Neurosci 2002 Apr 1;22(7):2816-2825