One thing to keep in mind is that the angles that the top and down tubes make with the other tubes at each end will need to change a lot if you are going to add 4" to the top tube. This means that the down tube will need to be cold set down and if the top tube has any slope it will also need to be cold set..........and likewise the angles these tubes make with the head tube will change substantially.

In the end there is only one good way to do this and that it to remove and replace the top, down and head tubes. By doing removing the entire front end you can be sure that you won't load up the remainder of the top and down tubes on some funny way that will only lead to failure down the road.

It may seem like more work to replace the front end that it would be to graft some additional length onto the old one but in the end it will be the cleanest, most simple, and safest way to make it happen.


dave