Drilling out those plates looks like it will leave too little material between the hole and edge. That looks to be a 5/8" hole? Recommended clearance from center of a 5/8" hole to edge of plate is 1-1/8".
Also the mentioned potential for alignment issues, however the clearance issue between the springs and U-bolts can be corrected by shimming the bolts with steel tube.
2000 Ford E450 V10 VAN! 450,000+ miles
2014 ORV really big trailer
2015 Ford Focus ST