Does anyone have experience baking bread at high altitudes?

I got a slow-rise yeast bread cookbook for Christmas and made some decent white bread over the holidays. Now that I’m back from vacation, I’m living at high altitude (around 4,500’). I tried to make some bread recently (using this recipe) and it just doesn’t have the same consistency as before when I baked it at a lower altitude. It tastes great, but it doesn’t have the consistency to be used as sandwich bread. It’s too flimsy. It rose fine, and at the end of baking it looked done and there was that nice “thwack” when I knocked on the loaf.

I’ve done some Google searches and there seems to be some variation in the suggested adjustments. What have you found that works?