Here is a PDF link to some technical info for the Water Better housing you are looking at.
http://harmsco.com/pdf/IP_WaterBetter_FINAL0204.pdf You may be pushing the limits of that housing at 100gpm. They recommend designing a system at 70-80% of maximum flow for best efficiency and for extending filter life. The WB170SC-2 may be a better fit. It has a maximum flow of 150 gpm which equals just over 100gpm at 70%.
Thank you,
WaterFilters.NET