KingCloudian:
Such a great mod and adds a refreshing dynamic, but it is nearly impossible to make a farm out of spiders. They always stick to the a ledge if they are pushed off, perhaps making glazed terracotta a non-stickable block for spiders? This would stay true to how slimeblocks do not stick to them (glazed Terracotta) as well

I wonder if a config-defined blacklist would be possible for this feature, so certain modded blocks can be made non-climbable, or the entire feature could be disabled by leaving no valid blocks.

Yes, it uses Tags. Not sure whether I'll add a config to 1.12.