Depending on the thickness of the wood member and the height of the individual drivers, the frame may not be significantly in play. Make sure the tweeter has line of sight for sure. The woofers are more forgiving.
If you feel the frame is in play, you can always build a platform for the center. The platform can be as simple as a box on the floor or a well secured shelf hanging on the wall. It doesn't even have to be the full 26". You could just raise it enough so the frame lies between two of the drivers. It also doesn't have to be pretty but anything visible could be wrapped in some black velvet. Having the center tower raised might be better to center the dialogue in the middle of the screen but there is also something to be said for having the front soundstage at the same bed height for smooth panning. You can always try the different placements to see which you like better. Moving speakers around costs you nothing. You can use a side table to temporarily raise the speaker.
Marantz SR7013, Polk Signature S60s/S30/S15s/HTS12s, Polk MC80 (x4), AC Infinity T9/S9, AAB4 HTPC,...still to come - Panasonic DP-UB820K, 82" 4K QLED or eqv.
Last edited by Darren Chan; 11-19-2019 at 10:38 AM.