If I have the chance to buy new frames, I go with grooved top and grooved bottom boards. Snapping in the plastic is easy and quick.
This winter I've been rehabbing some old frames to renovate for sheets of plastic foundation. They have divided bottom boards. I horizontally nail the wedge bar with 3/4" nails that will also go through the plastic (elec brad nailer is a HUGE help) into the solid portion of the top bar. Then I also drive a couple of 5/8" brads, by hand, through the divided bottom bars which also penetrates the plastic.
It works pretty good. Basically I'm just getting too frugal in my cranky old age to toss these old frames away. By the time I'm done, I should have bought the new. Time is money, but I seem to have more time than money. And rahabbing old frames while watching NFL football games on a cold winter day in my heated shop is some of the best therapy I can afford!
I'm also taking many of the old brood frames and gluing a popsicle strips with the intent of going foundationless.
Grant
Jackson, MO