yea 40 players max with 7 SS. The SS you have chosen aren't cheap ones most of them the OT DT and LB can be cheap, DE's are middle area and WR and HB's are high , wouldn't have hopes for high contracts you should avoid low contracts, better have all medium then have high and low, so try calculating with all medium and if money left you can go high contracts
here you can see an example of 9 SS and 37 players
http://glb2.warriorgeneral.com/game/roster/161also on a side note you should try having around 30-40k left of wage for the second season off scale wages that nobody tells you about