Pipeline structure - predefined final estimator & stacked estimators

Hello,
is it possible with TPOT to:
1. make sure that the final estimator of a pipeline is a gradientboostingregressor
2. make sure that the final estimator uses, as stacked estimators, let's say an SVR and a linear regression
?

I see some predefined structure can be given to the pipeline, but didn't see how to satisfy my needs.
Thank you!