Well, I guess my methods on a few critters is “shade tree”.
I installed a supplemental transmission cooler on my 79 IHC Scout II. I used a “Kit” that may or may not have come with the cooler. Merely rubber hose and hose clamp.
I cut the steel line and spliced in the cooler. I went one step further sand double clamped the hoses. No issues, at all. As it had no way to measure and compare any temperature change, I dunno.
A few years later. Same technique on my 85 Ford F150 4x 4. Same story.
Years later, Jaguar lump time… The engine/transmission from the donor Cadillac came with the steel transmission lines. No added cooler this time. No tow work anticipated, unlike the Ford and IHC!
The lines were far too long!!! The Fleetwood Brougham car, much larger than the Jaguar SIII. I cut them just under the planned bungs in the radiator tank. I did not like the idea of a 90 degree bend there! So, I wrestled up 90 degree flared fittings. Double flared with my HF tool. I could have used steel. but, I wanted more flex than was available in the steel. I got another “kit” The flare to clamp fittings were straight. I needed 90’s. No problem, Used one of my tube benders. Voila, 90’s. Those went in to the radiator bungs. A pair left straight went into the brass 90’s. Hoses connected them.
so far, just fine no leaks, not even a weep!!
More than one way to skin………
OTH, my son has a beast of a forklift. Modded way back from a WWII Dodge weapons carrier. Bad hydraulic hoses. Same tractor shop that made up hoses for his ancient Case.
When my Jeep blew a Ps hose, easy. readily sourced at a Kragen. The fitting on the pump down in well. Ingenuity needed there, A tae for another day…