A film SLR is not a dSLR.
I shoot with two hands. 10 - 13mm less width means my left hand does not comfortably cradle the camera base. Right-hand grips aren't really all that relevant because almost all the camera grip happens with my left. Digital camera design requires use of the right thumb to manipulate controls so the right fingers have to grip the camera, thus dSLR's have a prominent integrated grip.. The K-5 grip shape allows my pinlie to slip off the bottom.
Comparing a dSLR ergonomically to an SLR doesn't take into account the fundamental change of operating method. I beleive it is more appropriate to compare a K-5 to a K10. So oif nly three fingers of my right hand fit on the grip of the K-5 it is smaller than I think confortable.
Again - it is just me and I know I'm against the tide on this.
Rather than too small, which is a judgement, I should have written something such as, "Smaller than I find comfortable or, "Too small FOR ME." With the film cameras, I rarely hold one for several hours without putting it down. I rarely shoot more than half a roll per outing. With a digital camera I/we can hold it by the right-hand-grip for literally hours and make literally hundreds of clicks. Many shooters find smaller and lighter is better under those conditions. I get it. <G>
W x H x D
K2DMD = 144mm x 92mm x 57mm; 685g
LX = 144mm x 90mm x 50mm; 570g
MX = 135.8mm x 82.5mm x 49.3mm; 495g
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K5 = 131mm x 97mm x 73mm including integrated grip; 660g
K10D = 141mm x 101mm x 70mm including integrated grip; 710g