But the 15-year-old from Hamilton - who now stands 6ft 5in in his stocking feet - has not allowed that to sink his sporting ambitions.
Inspired by watching Katherine Grainger win a gold medal at the Olympic Games in London, he switched from go-karting to rowing.
The Glasgow Academy pupil has made remarkable progress in a short period of time and is now well on track to emulate his fellow Scot.
He won three golds at the Scottish Rowing Championships at Strathclyde Loch in Motherwell back in June - just two months after first stepping into a single scull boat.
That success led to invitations to take part in the Scottish and British Sculling Festivals where he also achieved more noteworthy results.
Josh has now come to the attention of Scottish Rowing High Performance Co-ordinator Lee Boucher and his development will be monitored by him in future.
And the Glasgow Schools rower has admitted his ultimate ambition is to one day compete in the Olympics.
"It was quite a hard decision to give up go-karting last year as I had been doing it for so long," he admitted.
"I had been competing at junior level, which is for boys aged 17 and under, for four years and had raced all over Scotland as well as down in England and Wales.
"The likes of Jenson Button, Lewis Hamilton and Paul di Resta all started out in Super One. I watch them in every Formula One race.
"But I had been monitoring my measurements last year and could see I was growing and putting on weight.
"I gained about four inches in height during the course of the season. I knew I was going to be too tall and too heavy to continue with racing.
"In Formula One most of the drivers are around 5ft 8in.
"Jenson Button is probably the tallest on the grid at the moment at 6ft 1in.
"I was also weighing in at 152lbs at the end of the season. If you are above 150lbs then you lose time."
Josh continued: "I enjoyed watching all the success that British athletes had in the Olympics last summer.
"I was particularly impressed with the determination Katherine Grainger showed to win gold in the double sculls. She had won silver at the previous three Olympic Games.
"To persevere and win gold at the fourth attempt in London was pretty inspiring.
"My school has got a really good rowing system and I saw that we were doing well at it.
"I thought I would give it a try and when I did I enjoyed it.
"The average height of an Olympic rower is between 6ft 5in and 6ft 8in, so I thought perhaps it would suit me better and that has proved to be the case.
"I was quite surprised at how quickly I took to it.
"I now row two or three times during the week after school and do four sessions at the weekend."
The hard work paid off for Josh and he is hoping to enjoy many more victories in the future - including in the Olympic Games.
"Competing in events makes me work hard at my rowing," he enthused.
"I love to compete.
"I mainly do single sculls and I won the novice event at the British Sculling Festival in Nottingham recently.
"I was mostly competing against guys who were at university too.
"Lee Boucher, the Scottish performance coach, is going to give me conditions exercises and I will be part of GB training camps in the future.
"I suppose the Olympics is the ultimate goal. It is the pinnacle of sport.
"It would be amazing to be a part of it."