After around 18 months or so the Boars are mostly solitary, sometimes in brother pairs. It often seems they avoid the established sounder. Sows will attack them if they show up and she has squeakers, she may attack them anyway. I've seen what appeared to be epic battles between a lead Sow and a Boar, not much blood but a lot of action and noise. My conclusion is if you have a sounder regularly visiting your feed, the chance of a Boar showing up, if she isn't in heat, is reduced not improved.
If the Boar have a good natural food supply, no real reason for them to visit the feeder. Juveniles (1-2 years) are the exception and may drift in and out of a sounder some and are in transition from group animals to solitary adults.
Most times when I've seen big Boar it was maybe half an hour after the sounder showed up and started feeding, some times longer up to 2 hours. And most times the sounder circled up and the lead sow drove him off. In other words, they trailed the sounder and tend to show up late. If you shoot at the Sounder the old Boars aren't going that way
Best guess is if you get a shot at an old Boar it will be a one time thing, unless he is really hungry or trailing a Sow in heat.
Code blue (Sow in heat urine) may get you a shot.
I've had the best results putting up a scent cone and hoping a Boar gets a whiff of it. I've used chicken bones and leftovers from Kentucky fried or road kill, in a bucket and hung off the ground in a bush. I've also had good luck spraying down a bush with Nuc Mom (Vietnamese fermented fish sauce). Nuc Mom is to be handled like toxic waste. I had one leak inside my Jeep, it stank for a year. I'd put up my bait away from the feeder, but still close enough for a shot. My cousins favor Corn soaked in Beer, they save the last inch or so of every beer and dump it in a trash can half full of cracked corn. Protein seems to work best, it is in short supply in the wild.
Been my experience, unless there is a Sow in heat, Boar (over 2 years old) kind of show up when they show up and aren't real predictable.
Another tactic you can try is following a Hog trail after it gets hot out (mid morning), Slow and quiet. Look for brush piles or brush filled drainage ditches, or hollows. The Boar sometimes trail the Sounder (a half hour or more behind), the Sounder is headed for their favorite bedding area, the Boars find a likely spot half way and bed down somewhere near the trail. Be prepare for a quick shot.
Remember the Boar tend to be rear end Charlie and trail the sounder by quit a bit, if at all.
And my standard disclaimer, there are no real rules, just tendencies.