Helholtz Resonators DIY Input

I am very intrigued by @mahgister success with DIY No Cost Helmholtz Resonators and feel he is really onto something. I have read the past posts and have made 6 of various glass bottles and containers from 500ml, 750ml, 1.75ml.  Bottles are filled at 10% volume, straw lengths are 2-4 inches (longer for larger bottles) with 1/2 inch exposed out the top with a straw opening diameter of approx 1/8 inch.  They do seem to alter the sound in a positive manner but I wanted to reach out and see what improvements can be made.  Any input on the following questions, realizing best locations need to be determined individually, would help speed up the process and improve the results

Are there any general guidelines/rules that should be followed by all such as:  
     Best type of bottle material to use. Glass, ceramic, plastic?
     Use all the same volume size containers or vary sizes? Are there ideal sizes? Max size?
     Any Ideal straw sizes (length/diameter) by container size and length exposed out top?
     Are smaller volume containers best for high frequencies and large containers for low frequencies?
     Are there any required locations that would apply to all rooms.  Such as in corners, in front of
       speakers, behind speakers, at listening level when possible etc.
     How much liquid is best?

Any  input on these questions or general input from experienced individuals  who actually use Helmholtz Resonators would be appreciated.

Please this is a NOT a discussion on whether they work.