2 questions about manual transaxles

Question 1-
Every now and then (maybe 1 out of 100 times or less) my car will pop out of 1st gear. It doesn't seem to pop out as long as I shift into 2nd and then 1st. It also pops out of 3rd sometimes, altough it doesn't do it nearly as much as it does in 1st... only 3 times since August. When downshifting, the gears will "crunch" a bit going into 3rd if I don't shift through 4th. What would cause that? And the fluid is full and clean/cables tight.

Question 2-
I'm thinking about making a dual engine Cavalier (mostly just an excercise in "See?, it is different") with 2 supercharged ecotec engines (500HP/AWD!) At this point it's at least several years off, but I figure as long as I'm asking about manual transaxles... Would having one shifter for two transaxles work, or do they have to go into gear at the same time? Meaning, would trans 1 not go in because trans 2 isn't lined up, and then once trans 2 is lined up would trans 1 not be able to go in?
If 2 ecotecs work, maybe I'll try 2 northstars eventually :grinyes:

1) Check your shifter for adjustment and adjust your cables... worst off your synchros.

2) I have no clue how you would work 2 transmissions with one shifter.

Everything seems good that I can check... I was thinking synchros (definately for the "crunch" downshifting into 3rd), but I didn't know if they would make it pop out of gear.