Reducing strain a MoBo is a solution to a problem that simply doesn't exist. Think about it .... what really is the significance of the 2 pound weight when you are applying the 60 - 70 pounds of clamping force recommended by cooler / TIM manufacturers ? The other problem that most peeps don't think about till they turn it on is with the AIOs that do edge the better air coolers is the extreme fan rpms (and the 60+dbA noise levels) required for them to do so. I have had vacuum cleaners that are quieter than those things.
http://martinsliquidlab.org/2013/03/12/swiftech-h220-vs-corsair-h100i-noise-testing/
Unless you are shipping a pre-built PC via FedEx Ground or some other gorilla staffed service the weight of the cooler is a non-issue. Back in 1366 days I saw some problems with one particular brand of MoBo but the offending party has since joined the big boys using industry standard PCB thicknesses ... they also raised their MoBo warranty from 1 - 2 years to the industry standard 3 years.
-There has not been a single CLC with 1 x 120/140mm rad ever made that can match the better air coolers. The fact that the $75-85 H75 can not compete performance or noise wise with the $25-35 Hyper 212 is a I think is mind boggling.
-There has not been a single CLC with 2 x 120/140mm rad ever made that can beat (> 1C) the better air coolers at comparable fan rpms and noise levels. The H110 and Kraken 60 do match or edge the DH14 .... but the Phanteks will top or match those and the DH15 and Cryorig R1 can top just about any of them.
-I have never seen or heard of a air cooler breaking a MoBo just sitting on a desk. OTOH, air coolers don't do this sitting on your desk.
http://www.overclock.net/t/1440506/my-corsair-h60-exploded-water-explosion
As for what the OC asked, I'm not sure how aesthetics and weight figure into OC'ing.....the H75 will allow a moderate OC, just not as much as a $25 Hyper 212.
From a technical / performance standpoint.....
1. Air coolers have better performance, better noise levels, greater safety and better pricing than 120/140 CLCs.
2. The Swiftech H220-X just rendered the 240/280mm CLC market obsolete with the H220-X..... With the H100i having an MSRP of $120 .... and the H110 at $130 .... the Swiftech just crushes everything in that price range:
http://www.hitechlegion.com/reviews/cooling/liquid/40870-swiftech-h220-x-open-loop-240mm-cpu-cooler-review?showall=&start=3
http://www.overclockers.com/swiftech-h220x-cpu-liquid-cooling-kit-review
http://www.xtremesystems.org/forums/showthread.php?289340-Swiftech-H220-X-Review-Part-1-of-2