SimpleRasterConfigurator problems

There are several problems with raster styles:

1) RasterViewer.get(..) returns null as a Symbolizer.. Later it leads to impossibility to persist style by SLDTransformer and following errors to load style:

java.lang.RuntimeException: Internal transformation exception
at org.geotools.styling.SLDTransformer$SLDTranslator.encode(SLDTransformer.java:669)
at org.geotools.xml.transform.TransformerBase$XMLReaderSupport.parse(TransformerBase.java:611)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(TransformerImpl.java:584)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:638)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:279)
at org.geotools.xml.transform.TransformerBase$Task.run(TransformerBase.java:293)
at org.geotools.xml.transform.TransformerBase.transform(TransformerBase.java:126)
at org.geotools.xml.transform.TransformerBase.transform(TransformerBase.java:114)
at org.geotools.xml.transform.TransformerBase.transform(TransformerBase.java:155)
at net.refractions.udig.style.sld.SLDContent.save(SLDContent.java:127)
at net.refractions.udig.project.internal.impl.StyleBlackboardImpl.put(StyleBlackboardImpl.java:224)
at net.refractions.udig.style.sld.SimpleRasterConfigurator.synchronize(SimpleRasterConfigurator.java:141)

2) Opacity value in RasterViewer is not persisted during changes of active layer in "Layers" view.

3) This problem is more related to rendering: at the current moment the buffered image of WMS layer is not cleared and newly loaded image is rendered on the top of old. If the opacity value of raster style is 25% - then images are overlapped with 75% of transparency..