Going to replace the expansion tank and flush the cooling system with distilled water till completely clean of old coolant, then going to use the FUCHS MAINTAIN FRICOFIN LL if i mixed it at 35% rather then 50/50 doing this reduces the engine temp by 15% and have approx -25 protection, only ever gets to -10 and thats rarely, anyone mixed the coolant at 35%, it is known that the higher the coolant mix the less the water absorbs heat and engine runs hotter, you views please

Do you have any problems with it running hot ?

Personally I would follow the manufactures instructions.
Not too much and not too little.

That then leaves some margin with others topping it up with water later on in life, or after the air has been removed.

No problems with temp, gauge stays at halfway evan when towing 2 ton caravan. Years ago it was 35% mix as I remember on early cars.

Depends on how the manufacture mixes.

Bluecol used to go further.
I reckon then keep it 50 50 these days? To make it simpler.