Slightly off topic, but if you are suffering from tennis elbow, check out a manipulative therapist/physio who is willing to look at your ribs.
Scoff if you want, but I was suffering from tennis elbow for a while, and went to a couple of physio who needled it, pulled it, strapped it, banged it and tried just about everything. Then I Went to our manipulative therapist who ignored my elbow, but raised my arm and prodded around in my ribs, found a sore spot, worked his magic a couple of times and voila, no more tennis elbow.
Worked for a friend who was a sceptic as well. I see a bloke in Adelaide, but thats even further than a decent tripod shop for you.
Back on topic, if you are willing to shoot from a lower tripod height then you will be more stable so you can go lighter with the tripod. Think about the balance of heavy lenses and cameras as well. I don't know Pentax gear, but if your longer heavier lenses have collars then they will balance better which will also help using a lighter tripod.