The spacer plate (also called separator plate, or restrictor plate) has an influence as to how a transmission shifts. Larger feed holes will fill the accumulators faster, and allow a quicker shift, and firmer to an extent.
Its only part of the story though, feed hole sizes, line pressure and accumulator setup all work together to affect shift feel.
Shimming the accumulator will also speed up the shift, but more-so comes with making it shift harder. Different upper and lower accumulator springs will change the starting and finishing pressure also.
You don't need a really hard shift to make the transmission last, but you do need a quick shift, especially at high hp levels. Shifts can be quick without being harsh.
From what I've learned from Dave @ TEP, the transgo kit is a good place to start for the accumulators, and he has a recommended range of feed hole sizes that works well from his experience. That gets you in the ball park, and you can fine tune (a little softer or harder) via the Force Motor Current tables in the tune.
