Argh!!! R1 vs cap4 hoodies…

If it were me, I'd go with the Cap 4 – it'll be more versatile. Not as warm as the R1, but quite a bit lighter. On trips where you would be wearing the layer while actively hiking, you can usually count on it being cold enough out at night to need synth/down insulation in camp, so you might as well save a few ounces on your daytime mid layer. And If you need more warmth during the day, you can always throw a windshirt/shell over it.

For the sake of versatility, the cap 4 seems a better choice. Admittedly I run hot, but I can't wear my R1 hiking unless it's cold enough out to be snowing. Even then, it's a bit much for me.

There's other alternatives to the Cap 4 hoody that are similar in function (i.e., warmer baselayer and/or thin midlayer) like the various merino hoodies (e.g., Ibex Indie… I think Smartwool might make something similar too).

In cooler temps, I'll wear my Ibex Indie as a thin mid-layer and let it double as my sleeping shirt if my base is all sweaty and/or wet.

I have both… I used them differently. As others have observed, the cap4 is designed to be very snug fitting worn next to the body. It's not intended to come on and off. It's quite warm when air movement is blocked (wearing a good shell), and VERY air permeable (seems close to my summer tech-tees) so with a shell open and a breeze lets me vent a good bit of heat. The R1 can be worn as a base, but I never do. Typically I wear a very light base and then layer the R1 over it when I need the added insulation. It's fairly easily for me to put on and take on the R1. It's warmer than the cap4 and not quiet as air permeable.

–Mark

If the jacket is really The Biznass, have you considered altering the fit (i believe "letting it out" is the term?) to better suit you? If you aren't MYOG inclined, I'm sure a seamstress could make short work of it if you brought her the appropriate materials.

Oh, and Cap4.

Sir Mix-A-Lot called, he said you're just his type of hiker.

I kid, I kid!

The R1 is really warm and surprisingly heavy. Since you don't sound like a person who is naturally freezing all the time, and you need minimum bulk underneath the shell, the Cap4 should do well for you.

Of course, I could always just drop a few pounds…….
Not that I WANT to sport the backside of an athletic Swedish guy. But it IS a nice jacket.

I bike commute thru Chicago winters and usually end up layering something like a Cap 1 tee, Cap 3 long sleeved crew over, and on top a WPB shell on the coldest and windiest days. I wear a thick fleece neck gaiter, beanie, and go overkill on the gloves. I'm generally freezing for the first few minutes but warm up quickly and usually overheat at some point, even on the 5/10/15f days. I definitely get too sweaty with any fleece top since I'm zipped up to avoid the wind/sleet/slush. This is considering I usually run super cold any other activity and day of the year.

I say go for the Cap 4… I think between that and the Ozo your layers will still be flexible enough to wear another tighter, lightweight base under both if needed.