You should be OK using the 35 ft. HDMI cable plus the 6 ft. drop. The HDMI cerftification limits a high speed rating for conventional HDMI cables to 25 ft. while many longer (e.g., 35 ft.) cables will have no problem handling 3D. For example the monoprice 22 gauge HDMI cables in the 35 ft. length will generally work just fine for 3D. You may be able to do a quick test before you even upgrade to a 3D projector. If your current projector supports 1080p/60 inputs then set your connected 2D blu-ray player to output in 1080p/60 and also turn deep color on if both the player and the current projector can support deep color. If you don't already have a 1080p capable projector then a 1080p flat panel display (if you have one) could be used instead for testing of the HDMI cable. The HDMI bandwidth for 2D video at 1080p/60 with deep color is the maximum for any current consumer HD format and is more than required for 3D. 3D video from a blu-ray is limited to 1080p/24 and with the "frame packing" signal format used for 3D only requires about 50% more HDMI bandwidth than for 2D 1080/24 and less than requried for 2D 1080p/60..
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