XofPL: PLEASE, ALL FORUM USERS - BE ADVISED THAT THE FIRST PART OF THIS MESSAGE WAS DELETED BY XRAY`S PEOPLE BECAUSE IT CONTAINED LINKS TO OTHER MANUFACTURERS PRODUCTS - I BELIEVE XRAY PRODUCTS` QUALITY CAN SPEAK FOR ITSELF AND XRAY`S PRODUCTS DO NOT NEED SUCH "SUPPORT" - THEY CAN DEFEND THEMSELVES - I BELIEVE MY ORIGINAL MESSAGE WILL BE RESTORED - OTHERWISE I WILL CONSIDER THIS AS SEVERE DISCRIMINATION!!!!
Penguin`s advantage is the ideal side ballance, but it was achieved for the price of much higher CG... If you put 6 cells and a 300 motor on your standard Xray chassis and put it on a ballance measuring tool you`ll see the perfect ballance - so if you can achieve this with a chassis where all the cells are on one side - then it is not necessary to struggle for the ballance any more! Racing on carpet with foams you`ll quickly get convinced how important the CG is... I underestimated this feature before I first started in a carpet race... After what I had seen on asphalte compared to Micro RS4 the Xray seemed to be totally roll-proof - during the race I quickly changed my mind... So if you want to be happy with your model`s performance on carpet surface - you`d better not buy chassis with center-mounting for motor
Even with side-mounting for motor you will still have to do some set-ups to make your model roll-proof on carpet 
I suggest the hardest possible foams - 50`s in front and 45`s in rear (Ellegi). The model will behave in corners a bit like a rally car 
, but you`ll avoid rolling 