I have just bought the GHL KH Director with slave doser set and got my first KH readings (now 4 of them at 7.5dKH) loving it so far!

However my Redsea alk test has given me 8.2 (and have used this successfully for over 7 years) for the same times.
I understand that consistency is key here but also would be nice if test of KH director & Redsea were closer together! To this effect I'm going through KH Dir setup up settings very carefully and have a few questions that I feel need addressing:-
Sample tube length: instructions mention adding dose tube length of 12cm to the 4mm (int dia) silicone tube lengths (in my case 29plus 16cm) and adding 7ml for the water filter and obviously de aerating tube. Making in my case tube volume of 13ml

Points to note:
• The GHL Dose tube diameter is much less than 4mm -probably 3mm?.....
• It is impossible to remove all bubbles from the supplied “filter” about 1cm of trapped air, at the same time this trapped bubble does not wander? So 7ml to add becomes about 6ml

My question: should this be taken into account in my case~ 13 ml becomes say 12ml? Or is it already included in the software as I suspect the doser only uses the tube length and a bit more to completely flush the system?

pH electrode calibration does not have any temperature compensation input:- should this be done at room temperature which in my case is 21 or at 25 degrees C which is my Tank water temperature as I do with my Sump pH electrode? I understand that by the time the sample water is drawn up it will be more like room temperature. -IS THIS IMPORTANT?

Can I swap round the stacking arrangement so dosing pumps sit on top of KH Director as in my case easier to have kink/sag less reagent tube?

I have drilled a hole in the Reagent bottle top making it slightly loose with tube to prevent vacuum -will evaporation be a problem at 21degrees over say 3 months?

I use silicone for sealing aquarium rubber gaskets rather than Vaseline -is this a problem?

What do forum members and Vinny think please?