I'm not the best adviser on this subject...
That being established, the major short come will be the actual preheated plat size 260x240.
ATX motherboards usually take up to 300 cm or more in length. Although not all the the motherboard area needs preheating, the motherboard itself takes it space to seat.
It's also over rated in power, nothing new, at full power draws 1200W.
See consumer reviews
here.