Does anyone run a level loaded shop floor and MRP?

We have forecasts for our machines evenly spread weekly.  We are cyclical and the major sales period for us is mid year.  We run an evenly spread forecast so we have enough completed machines during this time.  The issue we are having is that MRP keeps telling our buyers NOT TO BUY.  This is because we have many machines on hand during the early part of the year.  But that is ok, as mentioned we want inventory to be built early.  Does anyone know how to setup machines and the raw material so that a level loaded environment such as