I was thinking that the original jug would be easier to port since you can remove the covers,
I assume you mean easier than a 346 without the removable covers?
Easier to do the uppers yes but with the 359 and 350 the lowers are a convoluted shape and require more work than on a 357 or 346.
So which is really easier?
As I understand it, the transfers should narrow slightly as they go up, with the ports opening to the combustion chamber being slightly narrower than those at the bottom of the cylinder, to provide proper velocity and mixture.
I agree, this has been my understanding also. The shape of the curve leading into the combustion chamber also plays a big part in this as far as directing the charge across the piston.
I also thought adding thicker gaskets to the port covers would be a quick way to increase port volume as long as the openings to the combustion chamber were widened also.
Yes but there's still the question of if there's already sufficient volume and more velocity is what's need instead. Also you may be only assuming the lower transfer opening can be made large enough otherwise there would be no need to create more volume in the middle of the transfer than the lower opening can support.
IMHO if the volume in the middle is increased toward the outer wall and has more cross section than the lower opening, the charge will just choose the straightest path through.
It will not need to follow the outer radius and get the benefit of of being smoothly transitioned/directed out the uppers but rather go right up the inside wall and hit the top of the upper openings at a tangent before being pushed into the cylinder.
This would seem to act much like a straight up open port design, except instead of hitting a radius on top to help direct it out, some charge could then go back toward the (more or less unused in this case) outer/middle part of the transfer and cause turbulence.
If you were to follow/match the added outside area/radius with material added to the inside horizontal divider, then that might get you something...