Just my opinion but you really need to know the actual substrate temp as to not burn your stimmie.I suppose you could pre measure the sub temp then record the air(wall) temp and set in comparison. Maybe once a week you could check the sub temp just in case.
What about gluing 2 peice of wood together and putting on paper with sensor in it , wood could be 10cm long x2cm high joined making like a triangle once on the floor.
Hope this helps
