Yeah, you can use the channel lock/pliers method. That's taking a bit of a chance. Quite honestly, considering some of the input on this forum regarding broken fork studs, broken seat bolts etc...it's iffy recommending a tool that CAN damage the chain.
You likely have a chain breaker? You can use that to seat the side plate. It has a large enough bearing surface that mangling it is unlikely. Don't over compress the joint. Keep in mind that the pins may well push out of the inside plate in the process.
Do keep an eye on your master link clip. While aftermarket chain guides may improve the issue (wear of the clip), it will still happen. Well, unless you keep your guide blocks pristine, anyway. During the life of the chain, you will likely replace several clips.
re: predrilling the spare side plates
That's a good idea!!