This should be fine, I have mine set with +/- 2 although set at 6.5 and it works fineI just got mine yesterday and am currently using it in my kegerator as the damned thing keeps freezing. I put it to 5.5 C +/- 2C so that the compressor doesn't have to turn on and off all the time, is that ok or should I reduce the differential do you think?
Or you can use a thermowell to put your temp probe in, I made my own for 3 FV's quite a few years ago but you can buy Stainless Steel ones quite cheap now.Also found that it works well to have the temperature probe secured to your FV with an insulator (I am using a washing up sponge) so that you are monitoring the temperature of your beer and not the temperature of the air in the fridge.
I have just got mine today and set it at +/- 0.5 degrees, I think having a short delay set can't do any harm, if the fridge is efficient then the delay will just cancel itself out anyway I guess.I set mine +/- 1 degree with a compressor delay of 3 minutes...but then I have my temp probe hanging in the air, I know this is controversial. The air temp varies slightly and slowly and the liquid varies hardly at all.