Minimum width of square area for Spiderdemon not to freeze in vanilla doom?

The radius of Spiderdemon is 128 units, making its diameter 256 units. And I want to give it the minimum area to active. Strangely, in ZDoom, a square with even less than 256 units(240, exactly) width is able to make Spiderdemon active. While a square area with 256 units width will make the Spiderdemon freeze in PrBoom -complevel 2. The animation is still moving, but it can't do anything; like it's stuck.

Currently I set 288 units width to make Spiderdemon not to freeze. But I want to know the minimum width so I can make a hidden Arch-vile to resurrect the dead Spiderdemon easily.(I made the DeHacked that makes Arch-viles to revive Spiderdemon.)

The SpiderMastermind isn't stuck in a 256 square because your copy of ZDoom is out of date. Grab the latest devbuild in the usual place.

antares031 said:

The animation is still moving, but it can't do anything; like it's stuck.

That's because it is stuck. It cannot successfully move in any direction without entering a solid line, which also means it cannot turn, as turning is the result of moving for monster step movement.

268x268, though you might have to position it carefully. Its step distance is 12 map units.

(I made the DeHacked that makes Arch-viles to revive Spiderdemon.)

Edward850 said:

The SpiderMastermind isn't stuck in a 256 square because your copy of ZDoom is out of date. Grab the latest devbuild in the usual place.
That's because it is stuck. It cannot successfully move in any direction without entering a solid line, which also means it cannot turn, as turning is the result of moving for monster step movement.

I was using ZDoom 2.7.1, which I thought the latest one from zdoom.org
I tried the latest one from the link, and it acts just like PrBoom; stuck with 256 units width. Thanks for the info :)

rdwpa said:

268x268, though you might have to position it carefully. Its step distance is 12 map units.

I tried that, and it's still stuck. The lowest I got is 274x274, although I'm not sure that it's the minimum value.
Speaking of step distance, Is that possible to make the minimum width even narrower if I modify its speed from DeHacked?

^ The minimum required room for movement = the monster's diameter + length of his 1 step (= the "Speed" property in DEHACKED). In Mastermind's case, it would be a rectangle with dimensions 256x268 (268 = 256 + 12). Remember to place him to touch the boundary of the minimum rectangle/square, because if you put him into the middle of it, he won't be able to make a full step in either direction, therefore becoming stuck. Yes, monsters are limited to making full steps (as big as their Speed), and they usually won't make lesser steps when a very-nearby wall blocks their movement, but they will evaluate it as an impossible step instead.

If you are using dehacked, can't you just reduce the width of the mastermind?