Anyone use latex topper as a mattress? Hybrid matress options?

[racetech]

Fold out beds on my hybrid I just picked up are terrible. May as well lay on concrete lol. Im considering getting a 3" Laytex mattress topper to lay down over the stock bedding. Or possibly using a pop up camper foam mattress in combination with a topper. Anyone who has tried to make these beds more comfortable id appreciate to know what you have tried or liked. I prefer firm but supportive not memory foam or plush. Thanks