I have supplemented tumor lines with 10mg/ml Cultrex type 3 BME in tumors with low take rates. I generally inoculate tumors with 10 million cells/200ul

Inject into the duct instead of into the mammary fat pad. With nude mice, an estradiol pellet is usually required for orthotopic models. 

The estradiol pellet is also required for subcutanean tumors