I'm upgrading my 45x45x45 terrarium (housing 2 whites tree frogs) to a 60x45x90. Considering I only use a heat bulb and a daytime bulb, do I need to get the 60cm light canopy to match the width? I don't have a use for the 3rd bulb slot, but is it okay to use a canopy that doesn't cover the whole width?

Thanks!