You're going to have a difficult time doing that with whole trunks, as the point of the hugelkulture is to have *decayed* wood provide moisture and nutrients to the garden above. As wood decays, it actually absorbs lots of nitrogen an other vital resources for your plants, so putting a long-decaying wood into the beds will prevent them from reaping the benefits of *decayed* wood going into the ground below them.
You may be able to accelerate the process with a chipper and really rich compost, but there is a reason people use cedar for roofing, siding, and long-lasting mulch...
It is definitely OK to use lots of cedar. It will likely take longer to break down but if you make sure to have soil/compost/manure contact with all buried logs and you provide a more generous top layer of soil for planting into. The other thing I would do is to put the cedar in the deepest layer and use any/all other woods that will rot faster in layers closer to the surface
Some notes from using cedar fence posts. Young cedar with a lot of sap wood breaks down more rapidly than mature wood with more resin. Where there is already rotting cedar the organisms that break it down invade more rapidly. Therefore my recommendation is to use a mix of old fallen wood and young wood that is being removed for spacing. Perhaps place the rotting wood on top and woodland soil on that for inoculation. Pemaculture principle: observe what is happening in your wood lot. When, where and how does fallen wood break down. In my environment moss provide provides habitat for surface break down and fungus where it is in moist soil contact. In dry conditions or anaerobic wet clay conditions there is little decay.
I normally avoid western red cedar or redwood for hugels, but different species have different allelopathic effects. Are your talking about tamarisk/salt cedar? That is an old world tree relatively unrelated to North American species. If I wanted to grow a particular evergreen or its native associate species, I would use that tree’s wood, just like it does in the forest. The dead wood generally contains the fungal species necessary for healthy root/mycorizae associations necessary for many trees like redwood and western redcedar.
This is all just my opinion based on a flawed memory