I have been meaning to answer you:

The effect of gravity on humans has been of interest to me for some time and I try to stay as much abrest of the subject as a layman can.

Living for a period in 1/6th G would certainly be of interest but not conclusive. We know that the long term effect of zero G is devastating and we know that one G is acceptable and maybe optimal. At some point between Zero and one the body loses it's ability to stay fit and various bad things start to happen.

Rigorous PT can slow down deterioration at zero G but it seems that it is eventually a losing battle. For our voluntary muscles it probably has to do with action and reaction but for our organs it may be more complicated.

In other words, If we can remain fit with reasonable excercise on the moon it would follow that the same would be true in a higher gravity environment. If the moons gravity proves to be unhealthy it would not follow that Mars would be the same since we know that somewhere between zero and one it becomes nominal.

The interesting question is whether or not there is a gravity more optimal than 1G. It is possible that 1/6 G would eventually kill us and 1/3 G might double our lifespan.

On the radiation question, I was talking about something I know little about. Based on some of the more pessimistic posts on this board I had gotten the impression that the radiation level was far more lethal than what it, in fact, appears to be. Based on Nicks explanation of the risk, I see no problem with radiation as it pertains to volunteers. You appear to be correct in your appraisal of this problem

At some point we would want to reduce the risk to colonists and their offspring to a more acceptable level. The placement of habitats in canyons has been suggested as a solution. It would only require sealing on 2-3 sides as opposed to 3-4 on the surface.