Placing a belt line the normal way (without your mod) puts the belts underneath spidertron harmlessly. Belt Draw collides with spidertron's legs and tries to use underground belts.
belt-draw-next-tier and belt-draw-previous-tier controls aren't localised.
Also I see you managed to get other tiers of belts working. Before 2.0.0, I was going to suggest that you track whenever the player puts a belt/splitter/underground in their cursor (ghosts included), and use that to update your "tier" variable.
