Now this could go horribly wrong Swimdaddy, so please take it as a discussion not a criticism.
With a 1.5hp pump and only an 18" filter a 90 deg in the return line may actually help slow down the flow a bit in your case which will aid the filter in removing the dirt etc better. I am all for saving electricity and therefore hard earned income so I try to avoid all 90 deg elbows, if an elbow is used I usually replace that with a 90 deg bend. I get away with using only 0.08 Hp to run a 12000 gallon pool.