I tried growing Hoya engleriana in semi-hydro, and it was not very happy.  I tried growing it very cool, and it was not very happy either.  When this plant is not happy, you will know it in a hurry as it will lose leaves in bunches leaving a lot of ugly stem.  Tomorrow I will give away the conditions that finally made my plant thrive.  Here is a frontal view of the blooms:

Hoya engleriana – May 2013