Following the suggestion of TrentValley at the Raleigh Twenty site, I attempted this modification using a 28.6mm seatpost clamp. I got the Sinz clamp, because it looked like the shortest clamp. I dremeled off the lip so it would go down onto the steerer. I used a Tange Technoglide TG32STR threadless headset because it looked to have a very low rise. With that combo, I was able to install the headset without cutting the headtube. With the seatpost clamp and both nuts from the original Raleigh headset, I expect this to remain tight. I did find that installing the quill stem with the seatpost clamp tightened was not possible.