I bought an ignition from Ralph (RCexcl), and tested it vis-a-vis a vlach ignition.
The chinese ignition has a very nice advance (or rather, delay) curve between 2000 and 4000 rpm. In the Vlach the range is much shorter.
The chinese ignition fires at full speed (tested up to 10,000 rpm) like set. Above 500 rpm, delay gets to a max of ~22 degrees, so when set at 28 degrees, the spark will be at ~6 degrees when starting. A lazy flip like the Vlach allows, will kick back the prop, because then the timing is at full advance.
Ralph is dead right in setting these ignitions at 28° BTDC

The Vlach ignition works with advance.
The advance sets in at ~1900 rpm, and is at full at ~2500 rpm. This makes the engine rpm a bit sensitive around this mark.
Advantage is, that even a very lazy flip will never bite you.

Side note:
Because I had to bare the HT wire for my voltage clamp to work, strange things started to happen in my work shop.
When testing the Vlach, the transmitter and receiver I used to regulate rpm on the electric test motor went wild! My Schulze battery charger made clicking noises switching on and off. This was about the same experience I had when testing automotive appliances for radio disturbance resistance. These high power radiations play games with our electronic devices like transmitters and receivers.
So be careful to not damage the shielding in any way, or you may crash your plane.