Understood. That makes a lot more sense. I was thinking more of just covering the basics of it as a general all around application, but seems like you've done your homework in this. Haha.
So, you are correct in that for canopy penetration, having two straight down does work better. For the most part it has more to do with the solid mass droplets' speed, and how there is less distance to travel to hit the target. (Just as a general thought, think of the droplets/spray hitting it's terminal velocity somewhere between 16-18 inches, so spraying straight down gives you the closest spray to the target.)
So, given you know exactly what you are trying to achieve, I'll answer your question head on.
Overall the 80 degree tips, if sprayed at the typical heights as you might be spraying with the rest of your 110° tips, would not give you 100% overlap. Not a huge issue, as you spraying into post-emergent corn, and the tip spacing would do more for your overlap/coverage than a wide angled spray tip. Since you are on 15" spacing, I think this would be a reasonable trade-off for your corn. On your aphids in beans, I'd suggest staying at 110° all the way through and trying to stay closer to the ground.
So, for your tip selection, based on your input flow rate for your tips, it might be easier to select the tips separately through tip wizard, breaking down the distribution of flow between the two tips with the assumption the front tip is still doing most of the heavy work.
For example, if we are wanting to apply with your 14MPH, 15" spacing, 20GPA.
Assuming you'd still want something like 2/3 of the volume going out of your BPW/PWM nozzle, then simply split up the application rates by that same amount. This would make it simpler in that you'd have to pick two tips that just operate at the same pressures/speeds, just for different flow rates.
So, splitting the 20GPA into 13.5 GPA and 6.5 GPA, we'll entrust the 13.5GPA tip to the BPW system, and the finer tip to the standard auto-rate controlled nozzle body.
Tip Selection process for 13.5GPA tip:
When using Tip Wizard (for PWM systems) and putting in your inputs (13.5GPA, 400VMD, 14MPH, 15 INCH spacing, 110°), it shows the following (among others, but below are my preferences):
MR 110-05 @ 60PSI, with speed range of 2-17MPH, with VMD of 400
This would mean a duty cycle @ 14MPH of ~82% (just dividing 14MPH into the Max 17MPH)
On the duty cycle side of things, it's not too bad. (Usually I'll recommend closer to 70% to give you more leeway in your turn compensation through Pinpoint) Realistically though, as you'd need to slow down somewhat to turn, and you want to retain your BPW as well as your standard tips' pattern, that is a good spot to sit.
For the 6.5 GPA tip that will be running off of your auto-rate controller, we need to have it match up within that same speed range.
Running your input for that tip through Tip Wizard standard spray would show:
MR 80-02 @ 50PSI with a VMD of 254, while going 14MPH.
Given that is what you had found out yourself, kudos to that. Haha.
From that result, I might delve into something that a lot of people don't think about, or even know about. With all sprayers, there is pressure drop that comes from the plumbing setup and the tips. What I am getting at is that your velocity leaving the tip will be greater with tips that have less pressure drop.
Take it for what it is, but if maintaining that velocity leaving the tip is something you were wanting to accomplish, using a 'finer' tip would afford you more velocity leaving the tip. So, going from an MR80-02 to an SR80-02 would mean more velocity (but more driftable fines as well - which is a trade off you'd have to choose from).
All in all, I think you are at the right spot. Note that the DR110-04 might be a little undersized for your speeds and rates, but other than that, you have the right idea.
As far as the overall VMD recommendation for the tips, best try align yourself to the chemical/label droplet size category and then work from there based on your spraying conditions (i.e. wind alley, decent cover all the time, etc.). I'm not sure where you had gotten the 400VMD and 280VMD from, but just make sure it is suited to what your needs are.
Does that clear anything else up? I hate to answer questions that aren't being asked, so definitely let me know. There's just so much extra information out there, that its easy to get sidetracked.