Two linear passes is not enough. We recommend at least 3 passes in our Data Collection guidelines but even then you will need to up your along track overlap to make up for the lost coverage.
If you are using 75% across track overlap on two passes you will only bet getting 2X coverage on a stripe that is 3/4 the width of one image. Due to this you would need to up your along track overlap to 85%+ to get enough looks at the scene to reconstruct it.
Also, the longer the linear mission the more passes you are going to need to get it to process properly. Think of it as a table. Does a table stand on two legs? Nope. 3? Kinda. 4? Getting there.
The bottom line is you want about 15 looks at everything you want to include in your map.