I don't think I've heard of the internal method of joining.
I've heard some talk of a 'sleeve' type of joint for broken cantilevers, or a 'telescopic' method, inserting one into a stub or what's left.
I would think instead of an internal 'splint' most re-tippers would just replace the whole thing. The only hollow cantilever I've heard of is aluminum as I read that boron or beryllium tubes are no longer made.
I would just email the person and ask, or just find someone else.