Michael Schumacher\'s hopes of chasing an incredible eighth world title next year were given a boost this week as his Mercedes team made clear they are beefing up their challenge on and off the track. Mercedes are recruiting former Ferrari technical director Aldo Costa and the experienced Geoff Willis, most recently with Hispania, in a move that will increase the strength of their engineering and technical line-up at a stroke. And they are also sharpening up their approach to the teams\' Resource Restriction Agreement (RRA) by calling for full audits to make sure all of the top teams are respecting the rules and playing on a level field. Recent surveys have suggested some teams have broken the agreement. \"What we need with RRA is an independent audit of both the methodology and the numbers so we can all be comfortable,\" explained Mercedes team chief Ross Brawn, whose outfit, in a former incarnation, downsized dramatically when Honda pulled out of F1 at the end of 2008. \"We achieved that with the aero testing. We have a university in Switzerland that comes to look at all the teams, looks at their design work, looks at their wind tunnel work and checks they are achieving the figures that they say they are. And we must achieve that with RRA - as it is the only way we can stop these accusations and innuendo.\" Having signed Costa and Willis, he added: \"To add people you have to have the structure you need, and obviously one of the big things for the team is Bob Bell joining us. \"The infrastructure has to be in place before you can start adding numbers. And I think we\'ve strengthened the structure. It\'s always nice to do well with the smallest number possible -- and there is the RRA limit to consider -- and we are looking to move up to that absolute limit. \"At the same time the other teams are coming down to it because they are still on the glide path down to the RRA limit -- so in 2011 the teams who are bigger still have the benefit of that glide path down to the RRA targets.\" Bell joined the improving Mercedes team as technical director earlier this year after being released by Renault and his restructuring programme is expected to bear fruit in 2012. Costa will join Mercedes as engineering director and work alongside Brawn again, hoping to reprise the enormous success they enjoyed together with Schumacher when Ferrari dominated F1 and the German earned his soubriquet \'red baron\' by winning five successive drivers\' titles. Willis, formerly with Williams, British American Racing and Red Bull, joins as technology director. Brawn said: \"Having worked closely with Aldo for many years, I know that he will bring dedication and championship-winning expertise to the team when he joins in December. \"Building a winning team is an exciting challenge for us all as we work towards the competitiveness and standards that we aspire to as the Mercedes-Benz works team. With a strong technical structure led by Bob Bell, we are moving ourselves into the best possible position to achieve our ambitions.\" Mercedes\' announcement came after widespread recent rumours that, according to a study of the teams\' activity, Red Bull had breached the RRA limits. Red Bull have denied this allegation. Asked about this, Brawn said: \"What has been done so fair is just a benchmarking of the methodology, but not of the numbers. The process done so far is to check that all teams are interpreting the regulations in the same way - and it has been successful. \"But we believe it has to go deeper than that and we need auditing of the numbers because it is such a competitive element of what we do. \"Our cars are measured, weighted and checked. The amount of money spent is a very strong influence for your competitiveness and you need to have good control of it.\"