The HP in that model is appropriate for its size & weight, it's not underpowered. It's about the same power/weight ratio as competitors tractors. Looking at comparable kubotas the Massey actually has a bit bigger engine which should give it a bit more low end. 26 hp in a tractor that size is plenty, it works a bit different than lawn mowers or vehicles. It's got almost the same HP as an old 8N Ford which weighed 50% more.
It's got plenty of power for its size, not to worry.
