I mean, the issue would be in the structure of the cross validation approach. Say, set training = 29, test = 1, build models etc: how well did you do on the one

I mean, the issue would be in the structure of the cross validation approach. Say, set training = 29, test = 1, build models etc: how well did you do on the one? Rinse, wash hands, repeat 30x. This is your cross validation error rate. Its not that difficult.