So I've got this board someone else made with some cool LEDs on it (it's pinball related, no need to go into a ton of detail, though). He used some sort of kit sequencer board and there are ten outputs going to ten different LED strips and they "move" one at a time and you can adjust the speed. But they are straight on or off, no animation.
So I figured why not animate using an Arduino and PWM output. In absence of ability to do more than half of those at one time easily with what I had on hand, I wired up ten LEDs but just paralleled the top half with the bottom half, so I'm really only driving five outputs. And instead of one LED on at a time, I have two. I like this look better, too, so that part is fine.
The problem is the stuff I'm driving for real (I prototyped it with just a single LED in each spot) is some higher current LEDs and I need to use a MOSFET. The other problem is his current setup is common ground. I didn't notice that originally and ordered an Arduino Pro Mini and this shield for it:
Now, I'm pretty sure the only way to use that combo is to re-wire the LED setup to common positive, right? If I want to keep the current wiring setup, I'd need to build my own shield using P channel MOSFETs and an inverter on each channel (because inverting PWM in software looks pretty non-trivial, and is especially non-trivial to retro into the code I'm using now), right? If I did that I'd just do it on a proto shield for a Leonardo I already have, so that option isn't horrible, I guess.
Rewiring the original setup isn't that hard, just time consuming. And I had hoped to make it easy to put back the other way since I am planning on keeping the original sequencer in place anyway (it flashes a couple other LEDs and I like the hard on/off of those and figured I'd leave it to drive those).
Thoughts? I'm new to driving LEDs with PWM, so be gentle. 
--Donnie