My son wears my 661 elbow/forearm pads as knee/shin pads – as I don’t wear them on the kind of rides we do together that saved a few quid (or would have if I hadn’t bought kids pads first – they were rubbish and wouldn’t stay in place).
Swapping the Beinn’s 60mm stem for a 40mm required a couple of shims to get a stem at a reasonable price (1″ steerer and bars) – and it’s a stem I might use myself later.
I also swapped the layback post for an inline one – standard BMX sized post.
In total that took about 1.5 to 2″ off the reach – which is like taking 4″ off my bike’s reach. Made a big difference to how stable he was.
As he grows the original bits will go back on.
Islabike’s size charts are pretty good for height – it was just the reach that needed playing with.