The Wyberton-based team G&S Racing Kawasaki were at Donington Park for round four of the Stock 1000 and 600 championships - which were being run as a support class to the British round of the World Superbike championship on Sunday.
Both riders secured a strong result, with Fisher finishing 17th in the Stock 1000 and Van Leuven eighth in the Stock 600.
Fisher recorded a strong qualifying time to start the 12-lap race from the sixth row in 18th place and, as the race got underway, he immediately moved forward to 15th on the opening lap.
By lap five he was holding 13th position when the course car was deployed for an accident further down field.
When the car left the track two laps later he was pushed back down to 19th place and had to fight his way forward once again.
On the last lap he was up to 17th but ran out of time and was forced to take the chequered flag in 17th just outside a points scoring position.
Van Leuven began his campaign in the Stock 600 race from the third row but he got a terrible start and dropped down the order to 13th on the first of the planned 10 laps.
But he soon recovered and began to chip away at the riders ahead making his way forward to eighth on lap seven.
But his progress was halted by the red flag as a couple of riders fell from their machines.
With two thirds race distance having been completed a result was declared on positions at seven laps, resulting in the Dutchman being awarded eighth place and a further eight championship points.
“I was happy with the end result but the start was just terrible,” Van Leuven admitted.
“Then at the first corner Joe Francis had a high side and I just managed to miss him but of course then more people passed me.
“I must have been down in about 20th place by then but my pace was good and I managed to get further up the field.”
The next round is at Snetterton in Norfolk over the weekend of June 19-23.