I have a similar setup to yours. Here is what I get for volumes when I put in 11.25lbs of base grain.
Strike water 3.77g, Grain absorption 1.35g, Water available from mash 2.42g (first runnings), Tun dead space .25g, Sparge volume 5.07g, Est. Pre-boil volume 7.24g. Boil off 1.0g. Post-boil...