When had my roof top box I had floor grills in them aluminium / perspex baskets , best baskets I've ever had for training my birds and if was on a wagon with floor grills be fine , as for heat most these Geraldy wagons have good ventilation systems on them , the roof top box I had was never too hot and well vented if anything they'd of been a lot hotter in boot of car . Love or hate these baskets everyone will have a preference , I for one think there great having used them for quite a few years .Just have to ensure the birds are good enough to start of with , most look at racing problems to be everything else other than the birds in the basket , If birds are getting messed up in the baskets then solutions should be found to solve them like grills in bottom of boxes , gives birds something to grip to and cardboard in bottom will ensure droppings dry better . I've actually asked Geraldy for a price on 3 baskets as that's all I ever used and think there probably best basket on market .