Lot of factory installs used 6-8" length of hose to couple the lines to the cooler in radiator... As far as run hotter maybe .02*F...
no doubt... That also benefit absorbing shock to line however im saying if the entire cooling lines are rubber... Not just the ends
Ive used hydraulic hose on many of my engine swap cars. I try to find hose barbs that fit in the trans and the radiator and just use a good hose clamp. Makes running and hiding lines alot easier. Never had any problems.
Interested in why you put the cooler in the rear of vehicle? Hardly anyone uses hoses the full length from the trans to the radiator/cooler. I run a few feet of rubber hose to my radiator and external trans cooler.
I am running a aux cooler. I cut the lines close to the radiator and ran the aux cooler in series w/ the radiator.