The trick i use for this is that i get everything EXACTLY where it goes and lock it, i use the tensioner arm OUT of its hole, this gives you just enough room to put the belt on with next to no tension but still enough to not move everything, then with a bent flat head custom hook like tool i made, ill pull the arm in to its resting place putting tension on the belt once i get the nut just a bit on, then its a matter of finishing the job. took me a few times to figure this out, it saves me having to reposition the cam , i also have a custom locking tool that i made, i just took a long bolt and used it by cutting off the threads on the end but its loosy goosy by about 3 mm, i cut off the head of the bolt and just use it as a shaft, once i have the belt in place but need to tention things up i slide a piece of copper pipe i made fit over the bolt, split it down the middle on one side and rolled it to fit around the bolt, this makes a tight fit and put the IP back to where it needs to be but gives me PLENTY of room to work with things with the belt slightly slack, obviously i have the shim pipe in place when putting the belt on to start and i use some plastic clamps to hold it on the cam sprocket and the IP sprocket AND the crank Sprocket. this is a trick i say speeds the job up by about 10 minutes easily .