here a minivid with the 125mm i think it is 10mm
3holes = 125mm
4holes = 137mm
I never posted mines, I drilled 4 3/4" holes. They are 137mm cranks. I haven’t weighted them yet. I’ll do that as soon as my Schlumpf goes on vacation for the season 
Whoa, what size drill bit did you use? Was it a forstner bit?
I used these kinds of drill bits on a press-drill. I could have done it at my school with normal bits though. I’m in a welding school, we have pretty much every possible sizes
Yeah I was looking at that type, but didn’t know if they would drill holes into aluminum. What size did you use, and did you just drill all the way through or stop at a certain point? And did you have to drill pilot holes first? Thanks.
They do drill through aluminum, but they are worned out. I bought them on sale for 10$, and with my employee discount
I used the big one (3/4") all the way through. I drilled another pair that I use for Street, there’s 3 holes in each cranks and they are a little bit smaller. I have pictures on facebook, I can’t post them right now since I’m using my iPod.
I did have a pilot hole… But the press-drill wasn’t really good and it didn’t drill directly on the pilot hole.
I have also drilled my 137 moments with 4 3/4" holes. Works great. I used a smaller bit as a pilot and then stepped up to the 3/4" bit. I used a drill press and lots of cutting oil.
I wanted 3/4" holes but the largest (traditional) bit I had was 1/2". I was able to get 5 holes plus several smaller ones, without coming so close to the edge of the crank arms. So I probably got roughly the same weight savings with 5 holes at 1/2" than 4 at 3/4". 
Its quadric, not linear.
Cato
Yup. Cross-section area taken out with 4 3/4" holes is Pi * 9/16 in^2. 5 1/2" holes gets you Pi * 5/16 in^2 taken out. That’s almost double for the larger holes. 5 5/8" holes will get you closer but it’s still 14% less than the 4 3/4" holes.
Any high-speed steel (HSS) bit will drill aluminum just fine. Al is a relatively soft metal…
Yeah I just bought the 3/4 step up bit and finished enlarging the 1/2" holes I had initially drilled. Cut through like butta with a little motor oil. But for ultra light cranks, which I would use only for road climbing, CF uni cranks would be the ultimate! Just use inserts in the pedal & crank hole.
Carbon cranks won’t save you any weight unless you’re trying to reduce the size of your bank account/wallet:
http://americancycle.com/product/fsa-carbon-pro-bmx-crankarm-175mm-2941.htm
I have some Venture 165’s, weighed them last night, 422gm original condition, they could probably be drilled and drop another 50-75gm.
Sexy!
Is there a “Like” button somewhere around here?
Wow.
I’m pretty sure the spyder adds a fair amount of weight. And I would get 165’s not 175’s, so both those things would likely put the cf cranks in the 300-325g range, per pair. Plus, they’re just cool looking, and it’s only money…which isn’t worth much nowadays anyway! 
What do you think this is, Twitter?
If you “like”, here’s your link
I hope those cranks are REALLY strong. I still remember the day I was stoking uphill on a Trek MTB and one of the stock cranks snapped in half. At that point, my left shoe was clipped to a pedal with a 2-inch piece of crank attached. I took the bus the rest of the way to the office and got tons of laughs showing off one bike shoe clipped to a crank stub. Looking closely, you could see how some sort of oxidation had been at work on the metal for some time (I never knew that could happen to aluminum!), but there was no external evidence of it. Oh well…good laugh; could have been much worse-- no injuries, luckily.
I do wonder if the drilling mod is more aesthetic than practical. Does anyone seriously suppose that their performance will be significantly altered by shaving the equivalent weight a a typical bowel movement? If you have any excess weight on your body now, why not just skip dessert for a week? …curious. 