A 3/4" copper supply line feeds the baseboard radiator loop. Due to friction, where the copper pipe came from the basement through to the first floor (hole in floor was too tight) a pipe wore through and developed a slow leak. Right now I have it patched temporarily. However, asking for repair suggestions, one was to fix it by cutting out the faulted 3/4" section of pipe leaving the two good ends of 3/4". Soder a 3/4" to 1/2" reducer to both ends of the 3/4" along with a run of 1/2" copper. Connect the two 1/2" pieces of pipe with flexible tubing that fits over each of the short runs of 1/2" pipe and then clamp both ends. However, it struck me that by doing it this way, it basically reduces the entire heating loop to 1/2" instead of 3/4" supply - am I right this is not good advice ?

NOT GOOD ADVICE

the only correct way to fix the issue would be to enlarge the hole through which the pipe passes

'why is there never time or money to do it right, but always time and money to do it again'

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Cut the pipe above and below the floor, enlarge the hole, then solder in a new piece of 3/4" copper with slip couplings at each end.

quote; am I right this is not good advice ?

If it is a "continuous loop" system then, yes you are and yes it is "not good advice".