regenerator design for alpha model Stirling

[messthompson]

I am converting two 31 cc weedeater motors into an alpha
configuration by connecting the crankshafts in between the
cylinders. I am resleeving the cylinders to remove the intake and
exhaust ports.

I was hoping that anyone with knowledge regarding constructing an
efficient regenerator system could help me with data for dimensions,
temperatures and materials.

I am going to first use a cartridge heater next to the hot
cylinder. Would it be better to tap into the top of the compression
space to let the heater cartidge heat the air directly (internally)
rather than convection heating?

Also, I have seen info stating that an alpha model regenerator needs
a "heater and cooler" section in addition to the regenerator. Is
there any substance to this and if so, then what is the difference
between the regenerator and the "heater and cooler sections"?

Thanks, this is my first post
Scott Thompson