wvo diagram, along with some questions

[boise outlaw]

attached is my veggie oil system for my OM617 Toyota, i'm new to MB but have run one in a powerstroke for years. Here are my parts list:

35 gallon VO tank
20 gallon diesel tank
Facet 60302 12v electric fuel pumps
WIX 5 micron Spin on fuel filter w/ base
40 Plate FPHE (veggie side)
Ford Dual tank selector valve



So my questions are with supply/return. I have noticed a gap in fuel when i switch from diesel to veggie and have to wait for the pump to catch up or i have fuel starvation issues. Its why i've installed the helper pumps which i only engage for half a minute or so upon switching fuel sources. Also is there an "ideal return pressure" when burning veggie, i'm considering scrapping the stock FPR bolt and installing an adjustable FPR.