too bad you don't have a picture to show the pipe you made. I'm surprised to hear they handled badly. I had a Penton 125 that handled great but with the limited suspension would get ya in trouble real quick in the rough stuff. It wasn't lightweight but was solid as a rock and the frames never broke and pistons lasted a real long time.
I do have a picture around somewhere Jag, gotta go digging and scan it.
I thought the handling and braking was wonderful compared to my 1974 XL250, which was so much better than my 1967 Honda Dream. MX bikes improved a lot in those early years, and once I rode the smooth handling mono-shock bikes of the 1980s I knew the old CR had to go, rocket that it was. I made 2 pipes for the 74 Cr actually. First one was brazed together and did not hold up very well. Butt welds, constant cracks. Steel gas welded the second pipe and it lasted well. The diffuser pipe was shorter and sharper than stock, the belly much larger and longer, and the reflector sharper as well, that I remember. The silencer slipped over the reflector and belly to shorten up the assembly.
I got bit by the "bigger is better" bug, I bought an XL500 which I drove everywhere:
That's me about 30 years ago. Pornstar mustache. Faithful dog. Brutal 360 4bbl 4spd woods truck.
I put a ton of miles on that old XL500. The front tires show it. Heavy, sluggish but dependable.
Almost no mods done to this bike. Only a 90mph top speed but it gave 80mpg so who cared!
Replaced it with an 85 Yamaha XT600. Wish I had bought a DT200...