I too spoke with Josh this morning about the slight leakage. He wanted to overnite a cap to me but as I'll be out of town til Sunday afternoon I suggested I try the "earless" Hohopirates cap as well. I got home to find the usual 1/2pt or so of missing coolant. I cut the ears off my old cap and tried it, to find the cap no longer leaks, but I now had a leak around the overflow barb.
I replaced the OEM clamp with a stainless screw type and now have no leakage.
I agree with Clint that the capacity of the cooler is irrelevant. What matters is the efficiency and flow rate. I would venture to guess that my aux B&M cooler has very small actual fluid capacity as well, but since it's already in the circuit I left well enough alone. I believe we'll see the true benefits of this "upgrade" when triple digit heat becomes the norm this Summer.
Glenn