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I believe that you can actually reduce the height of the fins and get the same level of cooling,

Which CoolerMaster? When I get a few minutes, I'll put its details into my little model here and see what
theoretical performance you should get. If you know what pumping rate you can manage (litre/min or gal/hr, I'm not choosy), that'd be helpful too (otherwise I'll guess one).
I have simulations for waterblocks that have been calculated to have tiny fin dimensions  the limiting factors are actually pressure drop and flow rate.
You need a certain water speed (m/s) to get effective cooling. If your waterblock is smaller, then a lower capacity (m^3/s) will provide that, BUT the amount of effort needed to force it through the block will be greater. You'll notice this as a pressure drop across the waterblock. Now, if you assume that you'll get a pressure of 0 bar.g at the outlet, then you can reasonably expect a pressure of >0 bar.g at the inlet. Make the block too small and you get a huge pressure at the inlet  enough to pop seals maybe. Make the block too big and you need to pump water at stupid rates to get the speed up.
It becomes a tradeoff, and the deciding factor is your budget: how much can you afford to spend on metal? That determines the surface area you can afford. How much can you afford to spend on sealing your system against pressure? That's your upper pressure limit. How big a pump can you afford? That's your upper capacity limit. The best fit between them is the design you get.
The surface area curve flattens out  beyond a point, the benefit you get per cm^2 of fin area are pretty negligible. The point to aim for is the breakincurve, where it just starts to flatten out. Then you're getting the best value for money out of the metal you've got.