Asymmetrical kettlebell front squats & stairs...?

40 lb. bell in one hand, 55 in the other, swap sides every 4 reps...not sure if this is a good idea or not, seemed to put some strange pressure on my lower back in the bottom position. Farmers walk up & down 1 flight of stairs, swapping bells hand to hand every 2 flights...no issues on that exercise. Need to get another 55 lb. bell ASAP.