We did end up crossing at Calexico East and yes, if you're in the far right lane it's way too tight. I made it to the border OK, but my friend got too close to something and ripped off the back of her RV. The lower cover of her diesel behind the rad. Someone in line jumped out, recovered it, and brought it to her so she could stow it inside her rig...otherwise she'd not have known.
Me, I got up to the US area and the openings are sooo narrow, I scrunched my drivers side a bit because the cement and iron post was so low, I didn't see it being bothered by something higher that whacked my drivers side mirror!
Not a fun time. We did not go to San Luis because it would have taken two 180 degree turns off MX-5 to get to the border and I'm still learning how to drive a 60 foot rig. Also, when we got to where the first turn was, I couldn't find where everyone else was doing it and everywhere I looked didn't look like I could make it. Soooo....
We did not head to Lukeville because of one 180 degree turn, AND the fact that the road is very remote with what appears, from the maps, no towns for miles and miles. My traveling partner was worried about getting help on the road if one or both of us had a breakdown.
So, we used Calexico East crossing. And next time, I'll be in the center lane until the last moment (RVs end up in the right lane eventually). Meanwhile, we both have damage from the crossing. Hers is much worse than mine. All I have to do is replace a marker light that was scraped off, and to remove the yellow paint from the stupid post I scraped. If there's body damage, it's hard to spot.