Arrangement of inlet & outlet valves on CH radiators

[Elrose]

Generally, in diagrams, illustrations, etc, the feed & return pipes are depicted at the bottom of radiators. Are there any limitations to fitting valves to the top ports ? This would greatly simplify my fitting of a drain cock to a lower level radiator. Thank you. Tony

 

[gas4you]

This is an old method depicted as TBOE. The flow goes in the top and thr return comes out the opposite side at the bottom. (top, bottom, opposite end)