The solid block doesn't need to be immediately behind the portal block. At higher speeds (for example maxSpeed 100) the block can be 2, 3 or more blocks away from the portal block and it will still stop your momentum.

This ofc doesn't make sense since the minecart went through the portal before it could have collided with the block.

Steps to Reproduce

• Set minecartMaxSpeed to 32 or higher
• Build a rail track leading to a nether/end portal
• Place a solid block immediately behind the first portal block the minecart will encounter
• Compare the results with and without the solid block

Observed Results

• When the solid block is present you appear on the other side of the portal with no momentum
  end portal(1).mp4
  nether_portal(1).mp4

Expected Results

• You would keep your momentum