In electron beam projection systems there are competing requirements for column length. Shorter lengths lead to reduced space charge interactions while Longer columns allow larger field sizes. Other parameters include the convergence angle and beam voltage. We have used a generic 4:1 reduction telecentric system as a test vehicle to study these tradeoffs. To determine the lens aberrations we employed a thick lens configuration with constant magnetic fields; space charge blur was estimated with a Monte Carlo simulation using a thin lens approximation. For a given beam voltage V, held size F, convergence angle alpha, and current I, there is a maximum value of column length L that satisfies a given resolution requirement. For example, if V=100 kV and 1=20 mu A then L must be less than 30 cm for 100 nm resolution. The use of a retarding field just upstream of the target can lead to greatly improved performance in terms of resolution, field size, and throughput; e.g., the minimum resolved feature size is approximately proportional to the ratio of landing voltage over beam voltage.