I would reckon your tripod is fine for lenses up to a couple of kilos or so. The strength ratings of tripods for me are pretty meaningless - it's all about
rigidity and how its being used. Any issue with your soligor 450mm will be due to its length, not weight, its not that heavy - what I refer to as bendy ruler syndrome, an inherent tendency for a long thin object to wobble and vibrate. You should check out some of the u-tube videos discussing things like weighting the tripod.
I customise plates for long lenses (this pic
here shows the use of a cheap macro rail on the heavy and way out of balance tamron 200-500mm) so I can get them balanced - counters sag and wobble. However one counter point is that shutter/mirror related vibrations are best militated against by mounting the tripod at the camera - locks the camera down. If you suspect camera related vibrations then you can get tricky with two tripod or tripod + monopod set ups, dampening with sand bags etc