I basicaly agree that the majority of files of less than 1Mb are infected
Now to help you all i have compiled a list of known infected less than 1Mb files, (This won't be all sizes out there but its a good start) hope this helps , 69.4 Kb ,134.5 ,174.7 ,399.0 ,424.3 ,628.7 ,765.5 ,851.7 ,972.7
Please feel free to add any you find , an up to date data base will help save many people grief and wasted downloads