Astros manager Bo Porter plans to experiment with the team’s designated hitter position during the second game of the season. Normal starting catcher Jason Castro is expected to hold the DH spot and bat seventh Tuesday against the Rangers at Minute Maid Park, while Carlos Corporan will catch starting righthander Lucas Harell and bat eighth. Normal third baseman Matt Dominguez isn’t in the starting lineup. Brett Wallace is set to play third, while Carlos Pena will play first and bat third. The Astros (1-0) are seeking their second consecutive win to start a season for the first time since 2003. The Astros defeated the Rangers 8-2 Sunday in MLB’s season-opener. [...]