You'll probably be dealing with less flux applied - and less as you move up the barrel from the bottom to top. Flux activity & No-clean vs. RMA vs. OA considerations are something to think about. Appropriate sized/patterned nozzles for your application that are kept clean are a requisite. If the spray fluxer sprays back and forth (perpendicular to the rails) then it will be more sensitive to belt speed changes than one continuous head of foam - be sure to verify consistent coverage. Pressure is something easily monitored - be careful about blowing out loose components if you're not clinching. One "tool" that I saw was an option for a removable clear flux window on the WaveSolder Optimizer - you run it through with the wave off and then measure the weight and subtract it from the "unfluxed" weight + you can check for even coverage at that point. You can still check specific gravity but it shouldn't change much if your drawing from a closed container - if you're thinning you flux for some reason then you need to verify it anyway. My 2 cents, Mike Sewell