Bulge '44 - Movement Wrinkle

[Xerxes77]

Engineer bridges are Heavy and use primary road movement costs for all unit types.

Thank you for these answers. Are they in the manual somewhere, or do they reflect knowledge accrued over the years?

After some tests, I believe Eng Bridges actually work as Secondary roads? This means they're affected by movement penalties imposed by ground conditions.

This would explain why the tank crossing the Eng bridge in the OP's video (at around 21:40) spends 6 MPs-- 5 for tracked Secondary movement (Primary cost is 4) + 1 MP for 130% Snow penalty (rounded down).

What I CAN'T figure out is how stacking works as regards road movement. In the example, 310 engineers are holding the bridge in a forest hex. An armored unit of 24 tanks coming from the rear using road movement can enter the hex for 6 points. The total now goes up to 550X men, exceeding the scenario limit of 350. I would have assumed road movement was not possible. Worse yet, I can still move in another 6-vehicle unit (total 610X) using full road movement. Do bridge engineers and/or vehicles somehow count less than regular units for stacking purposes?