I'd probably grab a pack of #5 Owner Hyperwires for the Wag Tail Soft Series and the Baitsmith. For the Slammer, a pack of #7 or even #8 would be good. Some Slammers have larger screw eyes on the belly than others, and it can be hard to get a smaller ring over the eye without damaging it.

Re: rectangular split rings on the Slammer, I will ask MS next time I talk to him what's the deal on that, or maybe he will just post and explain :) I am sure there's a good reason for it. Lucky Craft has been doing those type of rings for quite a while, and I do like them on my rattle traps and such.