Hi basil, he's still limping a bit, but fine in himself and it's more a case of us having to try really hard to keep him quiet, than him not wanting to charge about.
Great to hear Fitz has shown such a vast improvement since his op. That's exactly why I say there is no one-size-fits-all answer to the spay/neuter question, what's right for one dog may not be for another and you obviously knew what was right for your boy and made the right choice.
He won't be that prone to weight gain at this age, as he's still growing and expending plenty of energy being a lively pup. It's when they hit middle age like Lurcherboy (who has most definitely developed a case of middle-age spread in the last few months, despite no change in food intake) that you need to really watch their weight.
Pip had a go at Lurcherboy last night!
I ordered a kong wobbler and buster cube for them, that arrived yesterday. Put a handful of kibble in each and put them on the floor. Pip approached them first, then when Lurcherboy came towards them Pip showed him his teeth and snarled! I was so shocked, he's never shown a hint of aggression before and they usually share treat toys and antlers quite happily, if anything it's usually Lurcherboy that does the telling off if Pip tries to nick his antler. I put Pip behind the dog gate and let Lurcherboy have the toys for a few minutes, then when the cube rolled near the gate Pip had a go at him through the bars.
Seems like my pup is starting to grow up and try and enforce his place in the household. 
I was a bit worried leaving them for the school run this morning, as without his green feeder and kongs Pip makes a right racket, but I left his usual stuff and put down a treat ball and the buster cube for Lurcherboy and there was no trouble at all. The only thing is, they hadn't managed to finish anything other than Pip's green feeder, so I'm not sure what would happen if one finished and the other had some food left. Need to keep a close eye on it and see if it was just a one off, caused by a high value item (being brand new exciting toys with food inside) or if I might have to look at leaving them on different sides of the dog gate when I go out.
I have been challenged by ds2 and dd to teach Pip to tidy his toys into their box by the end of the day! 
We've made a start, although cheating really, by catching his toys in the box and then giving him a huge fuss when they landed in there. He definitely made the connection and within 10 minutes was dropping them in when we said 'in the box'. Need to get the clicker out now and do it properly or I'll be in trouble when the dcs get home! 