The differences in distributional patterns between benchmark data and real-world data have been one of the main challenges of using electroencephalogram (EEG) signals for eye-tracking (ET) classification. Therefore, increasing the robustness of machine learning models in predicting eye-tracking positions from EEG data is integral for both research and consumer use. Previously, we compared the performance of classifiers trained solely on finer-grain data to those trained solely on coarse-grain. Results indicated that despite the overall improvement in robustness, the performance of the fine-grain trained models decreased, compared to coarse-grain trained models, when the testing and training set contained the same distributional patterns \cite{vectorbased}. This paper aims to address this case by training models using datasets of mixed data complexity to determine the ideal distribution of fine- and coarse-grain data. We train machine learning models utilizing a mixed dataset composed of both fine- and coarse-grain data and then compare the accuracies to models trained using solely fine- or coarse-grain data. For our purposes, finer-grain data refers to data collected using more complex methods whereas coarser-grain data refers to data collected using more simple methods. We apply covariate distributional shifts to test for the susceptibility of each training set. Our results indicated that the optimal training dataset for EEG-ET classification is not composed of solely fine- or coarse-grain data, but rather a mix of the two, leaning towards finer-grain.