The German-based team ramped up its test programme last month, with two significant gravel tests in the south of France.
All three drivers - Chris Atkinson, Juho Hanninen and Bryan Bouffier - were testing the i20 at both rough and smooth dirt venues in Chateau Lastours and Mazamet.
While Nandan admitted to teething troubles, he said the were no significant concerns over the pace of development for the car which will be competing in the French Alps in just six months.
Nandan said: "We have had a lot of work to do in a short space of time but I can sense we are working well as a unified team.
"We have attained another important milestone by kicking off our gravel tests but we have more still to do in the remaining months before Monte Carlo.
"We have hit every target so far and I am proud of the entire team effort. We look forward to our next phase of development with optimism.
"We have had a very solid month of testing and learned a lot about the performance potential of the new Hyundai i20 WRC in a range of conditions.
"As with any inaugural testing, there have been some teething issues to overcome but this is precisely the purpose of testing and we have taken time to analyse and understand the problems."