I have a K 3 and K 5 II both set up as follows:
my full set up is a Opt/tech USA Utility strap
OP/TECH USA Utility Strap-Sling
OP/TECH USA Utility Strap-Sling (X-Large, Black) 3501262
plus a Joby Pro Series Hand Grip with UltraPlate
Joby Pro Series Hand Grip with UltraPlate 208 for DSLR JB01349
plus Joby Camera Tether for Pro Sling Strap
Joby Camera Tether for Pro Sling Strap JB01307 B&H Photo Video
both the hand strap and the utility strap are fastened to the top right attachment of my K 3 and K 5 II cameras and the ultra plate is attached to the battery grip
Grips (Genuine Pentax) - Pentax Camera Accessory Review Database
that is attached to the base of the cameras.
the camera tether is attached to the top left attachment for extra security.
I use the hand strap to keep the camera from swinging too much as it hangs off my right hip and to lessen the weight on my shoulder/neck as necessary. I some times carry the "big guy" the HD Pentax-D FA 150-450mm F4.5-5.6 ED DC AW
Read more at:
Pentax D FA Zoom Lenses - Reviews and Specifications - SLR and Interchangeable Lenses - Pentax Lens Reviews & Lens Database
I can quickly detach the sling if I want
I can replace the battery on my battery grip without any problems, to get to the camera body battery I need to detach the battery grip.
it works for me YMMV
[I listed B & H only because of the deal members can get when buying from them - check with Adam for current details]
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You mentioned you didn't like the Op/Tech slings but you might be able to utilize their attachment systems to the strap of your choice and work out a similar system if you were so inclined.