A particular form of constraint is incorporated to Linear Prediction lattice filter models in the form of unequal-length delays. This constraint amounts to reducing the number of intrinsic degrees of freedom defined by the reflection coefficients without modifying the LPC order of the corresponding transfer function. It can be optimized by a simple exhaustive search scheme. Preliminary results show that the prediction error is slightly decreased with respect to a conventional predictor using the same number of reflection coefficients.