I think the question the OP wants to know is a little more then clipping in on hillls..If I understand him right its that the climb may be so long and or steep that he has to slow down and he is concerned that at a certain point he will loose momentum and balance and then fall, he therefore keeps one foot free in case of a need for a quick stop. I have a similar problem in the hills of Vt where 20 years ago I could make most of them but the last couple of summers I couldnt [due in certain part to age but most to weight gain]. Remedy, stay off them until you can gain strength or loose weight.. Ive lost more than 35 lbs since last summer and I want to loose another 15 before I take those sobs on this summer.