Fall, 2011: So I'd seen the F-701 in stores for a while, but never really paid attention to it. Sure, it's shiny and classy looking, but it was in the ballpoint section. And for the most part of the last two years, I've been trying to avoid ballpoints (other than you, Jetstream *wink*) at all costs. Then The Pen Addict put out another blurb about it, I think this was back in September. He mentioned going for the 701 more often than the Pilot Precise V7, and that's all it took. I picked one up after work and immediately loved it. The construction of it is pretty impressive. I could care less about the "plastic ring" by which so many reviewers seem to be profoundly insulted. Seriously, I spent six bucks on this pen, it's ok if there's a small plastic embellishment in one little area. It has heft (compared to the typical plastic barrel), it feels dense, and the click is smooth.
On to the F refill. I'll admit that it's actually a pretty decent ballpoint. If I were just using the pen to doodle or write casual notes, I could leave it in there and be happy. But I had to find something even better to put in there. So I began my search!
I ended up ruling out most of my preferred cartridges, because they all flared out too quickly. I ended up with 3 possibilities: the Pilot hi-tec-c slim knock, the Zebra TechnoLine, and the Uni Style-Fit. Because the Style-Fit cartridges aren't designed with a lip/ridge for a spring to push against, I knew it would take a bit more work to mod them. So I've set that aside as a future project. The Hi-Tec-C was the most interesting to add in, because...well...Hi-Tec-C. The Slim Knock line seems to be missing a little something from the classic version, and it doesn't come in as many colors, but it's still a champ. I did some basic tape-up models and knew it would work. Then I ordered my own refills, so that I could cut them and glue them, which I would not do to my wife's pen supply.
Once I got my order in from JetPens, I got out my exacto knife and cut off, I think 2mm?, from the back end of the Slim Knock cartridge. Then I grabbed the back cap off the default F-Refill. Now here I realized that the cap would not go smoothly into the Slim Knock's rear, so I found a worthless ballpoint refill sitting in one of my Reject cups, cut a 'transition' piece off, put the cap in one end, and taped it up tight to the back of the Slim Knock. There was a little trial & error to get the lengths just right. But once I did, it all came together perfectly.
Later that day I ran out, picked up a second F701, and modded another Slim Knock cartridge to go in that one as well. One black 0.3mm, one blue 0.4mm. I love this couple. Until I ran them dry, they were easily my favorite pen(s) to use. It's an incredible combination, taking the best from these two manufacturers.
Spring 2012: I've made it work using Coleto and Style-Fit refills. This makes things a lot simpler. These multi-pen refills are available in much greater variety. The only additional step needed is to make a "spring-stop," but this is pretty easy with a swatch of tape wrapped around the refill.