Yep, that's a frame bag. But let's ignore it for a minute. First I want to cover the other freak flags my dream build is flying. Most notably, the 2.85-inch tires. When we decided this year to rely on our favorite trail to inspire our creations, I knew immediately that mine would run on plus-size rubber.

Less than 20 miles north of downtown Los Angeles, standing 5,000 feet tall is Mount Lukens. Behind it, winding down 2,700 feet into Tujunga Canyon is an 8-mile hot mess called Stone Canyon Trail. It's a loose, narrow, often exposed, rarely flowy greatest-hits album of every style of rock section you can imagine. It's perfect for plus-size tires.

My canvas is the Devinci Marshall Carbon because of its 110-millimeters of rear travel and directly progressive leverage curve. The standard spec 130-millimeter fork got me thinking. Like nearly all plus-size bikes, the Marshall runs a 29-inch/27.5+ fork. The 2018 regular 27.5-inch RockShox Pike, however, fattened up enough to fit 2.8-inch tires while still stacking nearly 20 fewer millimeters of height from axle to crown compared to the equivalent 29-inch/27.5+ Pike. The devil on my shoulder pulled out his little red calculator and whispered in my ear, "You could run a 150-millimeter fork without changing the bike's geometry."

"That'd be sick!" Said the other devil on my other shoulder. "And at that length, RockShox makes a Dual-Position air fork. Think of how much easier the climb up Grizzly Flats would be with the fork dropped!" So I went for it. And while I was thinking about the climbs, I opted to swap the rear shock to one with a remote lock-out.

I went for alloy rims because mistakes can get costly when you're running 18 PSI on carbon hoops. The drastically offset drilling and inter-spoke milling drew me to the Mavic XA Elite 27+. The moderate tread on the Onza Canis tires is perfect for clinging to the crumbling, narrow ledge sections that punctuate the loose, rocky chutes of Stone Canyon. Also they're skinwall. Skinwall is cool.

For stopping, Code brakes offer more power than Guides but with the same modulation. For going, Eagle XO1. Really nothing more to say there. I'm running Sram's oval chainring because I've optimized my Marshall for steep, techy climbs, but I'm still not sold on the oval concept for all applications. The frame uses a press-fit BB92 bottom bracket. I prefer threaded, but Hope's PF41 connects its cups internally with a threaded sleeve, so I've got the next best thing.

The Marshall was just shy of fitting the 200-millimeter 9point8 dropper post I've been riding all year, but RockShox's new 1x lever made the 175-millimeter Reverb the perfect alternative. The Enve DH bar is one of the few 800-millimeter wide carbon bars that still runs a more comfortable 31.8 clamp diameter. Ergon's new GA2 Fat grips take that comfort all the way to my palms.

And, yeah. That frame bag. The coolest, ugliest part on this bike. No matter how loop into Stone Canyon Trail, the ride is too big for a single water bottle. Especially during the hot L.A. summer, when packs become the most uncomfortable but also the most necessary. A 70-ounce hydration bladder fits neatly into the bottom of the bag, with the hose tucked in just above it. And I've still got room for tools, a pump, a compact windbreaker, a couple bars and a turkey sandwich.

But I don't always pack it to the gills. With a light load, the Marshall can do things you wouldn't expect from a plus bike. You get a better sense of the trail than on longer-travel options, and there's a more defined base to the suspension for pumping and jumping. And although plus bikes are naturally harder to skid, the Marshall's firm platform makes the breakaway point relatively well-defined.

I've ridden the Marshall before. None of the aforementioned handling was a surprise. That 150-millimeter fork, on the other hand, was a bit of a gamble. I was afraid the extra travel's softer top-end would rest the bars too low. I added some volume spacers to help keep it from diving, and I even tested it using a 160-millimeter air spring assembly just in case. But with the frame's adjustable geometry in the low and slack position, the 150 length felt perfect.

The 27.5-inch fork also comes with a shorter crown offset than the stock 29-inch version. Reeling in fork offset got my weight on top of the front wheel where it can help dig it in. The extra travel was the biggest treat. Those rare flowy bits on Stone Canyon are more frequent on a bike this capable.

Two-position forks will always have their critics. The extra parts come with some extra drag, but much of it gets masked by the soft tires. Anyway, no other feature will have a bigger impact on a bike's climbing efficiency, and efficiency is at a premium on 27.5+ bikes.

It's also at a premium on long rides when I had my frame bag full with five pounds of water, food, and tools. That changes things. The bike is expectedly less nimble, but also less chattery. That extra sprung weight calms the bike down through Stone Canyon's worst. But I wouldn't have put a frame bag on a dainty XC bike or a slasher like the Evil Calling. It suits the nature of a plus-size bike perfectly.

The nature of plus-size has a broad definition. Just like the early days of 29-inch, plus-size is still evolving. It may take a while before they find their audience. I'm just stoked to be in the front row.