You do not need to maintain the humidity in the whole enclosure to 70%. Not that I advise this but as a child I raised a redfoot for 24 years on sand with not added humidity and he did fine with no pyramiding. Tortise lived 29 years just fine. Humidify the hide box. I use cypress mulch for my redfoots but do not leave it too moist as you can get shell problems with fungus. I have a hole 1 inch dia cut in the top of their hide box. Then I staple a large sponge to the underside of the roof. Then I can water the sponge thru the hole without disturbing them and the moist sponge keeps the hide very humid. I had a seperate hide box with no added humidity that they never used so I took that out.
Tom