Well, I think Crafty Spire also used to be listed as a 'harder' type, not technologist/red difficulty. Maybe that was an intentional change, to distinguish it more from Golemite? If so, I have to salute whoever was evil enough to think of that. It's really nasty. Unless the first planet you capture bisects the map (I didn't do that on purpose, I swear). As long as you own it, they aren't willing to path through it.
IIRC, the CPAs only pull from SF if they bottom out the strategic reserve, all barracks, and all defending ships. I plan to have applied a few armored warheads to the problem by then. I figure 3 armored warheads is still less AIP than a raid engine or black hole machine AI type would net me, and after that I don't think any more spirecraft spawn.
If I hadn't bisected the map, though, this would be a ridiculously guerilla-style campaign. Translocators are speed 152, so the SF isn't just practically invincible, it's also twice as fast as a vanilla SF would be.