Putting practice aid

I am making a putting alignment practice aid. The one made with PVC pipe shaped like a U.

My question is how much wider than my putter should the opening be.

hi
why not use a L bend than has a screw fitting and then you can ajust the middle part up to about 1 1/2 inchs.
bill

I do not know what you mean by L bend. This is 3 pieces of PVC connected in a squared off u pattern. Like this l_l

It depends on how accurate you want to get. I'd personally go no more than 1/2" of clearance on either side (1" clearance total).

hi
you can get a u bend and a L bend pipe conector the screws onto to the ends of the pipes to join them up, they have a rubber "O" ring in them. a bit like the ones you get for copper pipes. so you have two long pipes and two "L" bend connectors and a short middle piece.
the short middle piece can be ajusted but unscrewing the pipe and pulling it out a bit, i made one years ago out of pvc piping and got the fitting in b&q where i got the pipe. cost about £7 in all. also lets you change the middle piece for a bigger piece and use it for your chipping too.
bill