Guides fore and aft.

the car wouldnt be able to shift its weight around side to side so would be more prone to tipping over. also it probably wouldnt get around very tight corners.

Before long someone (Mr F?) will be along to tell you to try inox mx3 instead...(!)

Turn on the taps... wire taps help spread the current around the track more evenly which reduces reliance on the track joints...

assuming the track is nice and clean and shiny..... its probably worth considering upping the AMPS with a more powerful PSU to give you more oomph... std wall warts only put out around 1 amp... two cars on one scaley PSU will cause stuttering on larger layouts at the weakest conductivity points as resistance builds up in poor track joints.

adding a second PSU may improve things a little but not as much as a good bench PSU.

Thanks for your comments.