Fortune favors the bold. You're operating in high sec so you'll have to hope fortune reluctlantly acknowledges the bold-ish. Put up a Large POS. If you're going to do something, do it all the way. If you half ass it you will just get a half ass result. Large POS, hardeners, EWAR, and put some guns on it.

You may be a one man corp but there is nothing stating how many alts one man can run at a time. I recommend you train those alts to anchoring V and get station defense management. If someone comes looking for trouble, then give them some trouble. If you actively man your POS guns you're going to cause some headaches for would be griefers.

Use Medium and Small Turrets. Large fire XL ammo and are for shotting at capital ships. There aren't any capital ships in high sec so don't waste the resources on them.

Here's how you load out your POS. Put up as many labs as you can max out. Go ahead and drop an assembly array. What kind? I don't know, I'm not your business manager, do the maths and figure out what you can make money building. I'd recommend going for isk/hr not isk/item. After you have a plan on how the POS is going to *** MAKE *** you money, not cost you money, you have a legit reason to place one. Now that you have the CPU and Power you need allocated for production, onward to defense. Hardeners are fun. I use them. Guns are even more fun. I use those as well. Anchor and set up your guns to defend from all vectors of approach on your station. Don't leave a medium gun on its own/isolated. A smaller ship will just speed tank it and drop it, creating an even larger hole in your defense grid. Online what guns you can, stock them with ammo and leave the rest offline. If you get war dec'd simply crop short what research jobs are short timers and turn off the labs you aren't using. If you're paranoid, unanchor and put them up in a station. Now with your extra grid and CPU bring on more defenses. 24 hours is ample time to do this.

For the most part if you don't go looking for trouble nobody is going to bother with taking down a heavily fortified and well armed Large POS... it's just not something you do for fun unless you're a masochist.

Strontium Calthrates... use them just incase you do get reinforced but don't use the full amount. By using a different amount, known to you, you dictate when the POS comes out of reinforced, they will have to watch you like a hawk or assume you used the max amount and then they can't do the maths and figure out when it's vulnerable again.

Short version:
If you're going to do something, do it big.