Viton tipped float needles
Hello Craig,
Surrey cycles sell Viton tipped needles for the top feed type float chamber.
An alternative is to use the smaller bottom feed float chamber, similar to the type 29 float bowl but with the larger banjo to fit the TT9. I think that this type is not so sensitve to being out of vertical. The fuel level will be pre-set but if your carb is at a downdraught angle, the relative fuel height will change if you rotate the float chamber from front to back. A front position will lower the level and rotated to the rear will lift the fuel level. The same reasoning applies to the larger GP type float bowl but I think that you get less variation with the larger bowl because it has less rotation angle - the larger body diameter hitting the carb body sooner. See if you can borrow one of the smaller type to try.
What area do you live. Maybe I could offer help if you are not too far away.