Well, Dave, I guess this is not as I previously perceived it.
It's never too late to learn...
So those MDS engines that do have Schneurle porting, need the idle-bar on the plug because they have a junk carburettor, that produces huge drops that can dowse the glow element.
This seems believable enough...
ORIGINAL: Flyboy Dave
Bottom line....the baffle on the piston doesn't cause droplets of fuel to get on
the plug....rather it is for scavenging the cylinder....owing to the lack of
scavenging found in the later Schneurle type engines.
With the piston baffle, the intake is indeed sent up by it, to scavenge the exhaust gasses down and out through the exhaust.
It is also prevented from just going straight over the piston and out the exhaust port...
But as a consequence, fuel is thrown in the direction of the glow-plug. If the droplets are large, the element can be dowsed.
Schneurle porting does away with the baffle, since the ports are angled up and away (in) from the exhaust port, scavenging the exhaust gasses without resorting to a baffle. TST (Travasi Super Tiger) is similar, but the ports are placed similarly to a loop-scavenged engine and are only angled up, to achieve what the baffle does.