After long rides I get a little soreness in my palms and elbows. I've got a flat-bar hybrid, which may be slightly too small, but fits great other than this issue. I'm making a conscious effort not to lock my elbows while riding. Strangely it seems to happen more when I wear gloves, since my bike already has ergo-grips.
It almost feels like my palms are digging into the bars, like they're carrying more weight than they should be. Does this sound pretty consistent with a stem that's too short? I have no idea how long the stock stem is, but its flipped and only has a single 10mm spacer under it. The handlebar height is maybe 1 or 2 inches below the saddle height.