Just my comments to the above messages

Saddle security:
Simple solution is secure your saddle to the frame with cable ties - It just means that the saddle is impossible to remove without tools - you could also change the quick release for a nut (I have done both)

Where to carry a D-Lock:
I have 4 bottle cages and a pump, the D-Lock (Abus Granite X) lives on the front fork. I don't have low riders, but i do have the attachments.

A 4" section of 1" aliminum tube bolted to the lowrider boss and the dynamo bracket with the D-Lock attachment fixed to the tube - simple and effective.

I also carry a 2m (6 feet) Kryptonite cable for use with the D-Lock
(Lives in the pannier)

Valuables:
All money and cameras etc go in the bar bag which you simply clip/unclip every time, mine has a sholder carring strap, so it makes a good bag to go and see something. As for the rest of the gear - it's a problem. Either keep it with you, or at the place you are staying, most camp sites and hotels will look after gear