Can I increase the amplitude to be more effective (if thick skin to not feel much or get faster results)?

Amplitude is one of those areas that there's no one size fits all solution. With contract, you will need sufficient amplitude to penetrate the skin, so 14v+ is recommended. With remote, more amplitude does not necessarily equate to higher efficacy. In some cases, less amplitude will work better. Depends on the program and the individual. Usually one will have to try the same program using various values for amplitude only to find what works best.

From the perspective of the spectrum sweeps, 20v is required to provide sufficient amplitude to all frequencies being generated at once. Even so, the amount of power when using a wave cycle multiplier of 96 allocated to each frequency is just about .2v. Hence why this method is currently not supported via contact mode.

Please check the blog-How Much Amplitude Should I Use?
http://www.spooky2-mall.com/blog/how-much-amplitude-should-i-use/

For more details, please check the link:
http://www.spooky2.com/forums/viewtopic.php?f=39&t=5939