Hey Vorta, thanks for the heads up on the heat sinks - I was searching around for something good like that, but hadn't found anything close with nice big fins like that. I just submitted an offer, so we'll see how it goes - I'd love to update all my S5's to use then, but first I'll see how much of a PIA doing one of them is. 
One thing I was wondering about was the placement - if you see on the image with my thermal camera, those heat dissipation squares on the PCB are actually fairly cool, it's the surrounding area that really heats up. Here's a closeup of that area on one of the newer PCB's (the one in the test case is an older S5):
The actual thermal squares are running a cool 105-115f range, whereas the area immediately surrounding it is in the 160-180f. I'll be interested to see what kinds of difference they make - I'll try some with just thermal paste first and see what they do. I can't tell if those regions are cooler because they're more effective at dissipating the heat (I'd be surprised if it were that pronounced), or if there were a heat sink there if it would absorb and radiate some of that surrounding heat.
With your ducts, did you play around at all with sizing the ports that you're using to the sides? I know you have one with and one without the sides, but just wondering if you played with larger vs smaller openings. Also, did you play around with different lengths? Mine is 5.6mm but only because that's the thickest material I had around - I could easily just use multiple ones to get more length, but wasn't sure if the gain between 5.6 and 25mm would be worth it (I read somewhere that you reached peak duct performance at 25mm for case fans, but who knows).
One thing I was wondering about was the placement - if you see on the image with my thermal camera, those heat dissipation squares on the PCB are actually fairly cool, it's the surrounding area that really heats up. Here's a closeup of that area on one of the newer PCB's (the one in the test case is an older S5):
The actual thermal squares are running a cool 105-115f range, whereas the area immediately surrounding it is in the 160-180f. I'll be interested to see what kinds of difference they make - I'll try some with just thermal paste first and see what they do. I can't tell if those regions are cooler because they're more effective at dissipating the heat (I'd be surprised if it were that pronounced), or if there were a heat sink there if it would absorb and radiate some of that surrounding heat.
With your ducts, did you play around at all with sizing the ports that you're using to the sides? I know you have one with and one without the sides, but just wondering if you played with larger vs smaller openings. Also, did you play around with different lengths? Mine is 5.6mm but only because that's the thickest material I had around - I could easily just use multiple ones to get more length, but wasn't sure if the gain between 5.6 and 25mm would be worth it (I read somewhere that you reached peak duct performance at 25mm for case fans, but who knows).