Jen, As I noted in another post about short cranks, the most suitable for shortening are the ones that have relatively the same thickness throughout the arm. Older vintage cranks are a good example of that, most of those can be shortened safely, and yes, that's a relative term. As safe as the original, I'll put it that way ! A fluted crank "may" be suitable only if the non-fluted section remains a relatively constant thickness(see the Andel). Hollowtech cranks for example, are a no-go. Mark [MENTION=33931]Bikesmith[/MENTION]Designs explained how he shortens them with machinery, but I forget the details. The arm ends have a machined arc to them. Below is a FSA and SRAM road crank that he shortens to 150-153mm and costs $149 w/rings. I suggest just buying an already short/shortened crank as by the time you'd pay for shipping your crank to him to even see if they'd qualify for shortening, then you add labor, plus return shipping, you've invested a notable amount of cash with no guarantee the crank is even suitable. That money would better be invested in a new crank, in my opinion. Like these (do read the details, including BB type, and check the BCD so your rings can transfer, if applicable):
https://bikesmithdesign.com/Short_Cranks/vero.html
https://www.bikesmithdesign.com/Short_Cranks/apex.html
I have sets of these Origin8 cranks, available in wide variety of lengths. A good price to try them out.
https://www.amazon.com/Origin8-Alloy...000AOC5FO?th=1
This is "an opinion", but I don't think 160mm is short enough for you.. While 10mm may seem great, for your goal to feel that push-down-and-back to the BB, go shorter still, like 140-150mm. It may take a while to get used to it but no guarantees. You'll have to play with your seat height and angle for sure, as well as cleat position(backwards). With effectively short cranks, you may be able to remove your home-made seatpost forward extension. (Isn't that the reason you made it, to get yourself more forward of the pedal spindles ?)
Sort out the the crank first, then go about adjusting your forward reach. If you absolutely hate a short crank, you can shoot me
! I think you'll find them suitable however ! I tried the tip toe approach, going from 185's to 175's, then 170's. Not an appreciable effect I was being drawn to. I was too far back of pedals/BB. and I was being drawn forward, much more forward than I ever imagined. EVER ! So I saw Sugino made some 152's and just bought them. (Now I ride 150's) Bingo ! For reference, my floor to sit bone is 35-1/2 to 36". Speed speed speed, leg speed. The ability to push down and back over the spindle effectively and efficiently, which the shorter arms favor as with a smaller circle to spin you have less bodily movement. And no, you don't lose any power with shorter cranks ! From where I began with a Nitto S84 mega-setback post, to where I am now on a zero setback post, I've moved my saddle forward 35-40mm. This was after I had been riding the 150's for some years, but in a much more upright position. Now I'm way down low, lower than I ever remember being years ago. The lower I go, the more forward of the crank/bb I'm drawn.
Moving your feet forward over the spindle some as I referenced in the other post really helps to stabilize your entire lower body, to feel more connected to, or "in the bike" so to speak.
Like all of this, expressing it in words doesn't do the actual experiencing justice. There is no try, only DO !