Palindromic prime pyramids with step size 3

Step size 3 means adding three digits to each side at a time.  We give the last row of the tallest such pyramid we know of various starting values.  (Note: these were done with probable-primality tests rather than primality proofs.)

Often two or more pyramids are tied for tallest, so we give each of their last rows.   You can reconstruct the pyramids by deleting digits from each end of these last rows and stacking them up.

Starting with 5

7811119053243519581703581473417743783791043197591941237981753399353589421953429519189567423847509967743789511019703213383729851629487839383037151769191077927749903403293513611653127619017231507111627359929919719071651089303189811231707179617803717421049903811123003009271137003511411719419617101501003305033001051017169149171141153007311729003003211183099401247173087169717071321189813039801561709179199299537261117051327109167213561163153923043099477297701919671517303839387849261589273833123079101159873477699057483247659819159243591249853539933571897321491957913401973873477143741853071859153423509111187:

1181119053243519581703581473417743783791043197591941237981753399353589421953429519189567423847509967743789511019703213383729851629487839383037151769191077927749903403293513611653127619017231507111627359929919719071651089303189811231707179617803717421049903811123003009271137003511411719419617101501003305033001051017169149171141153007311729003003211183099401247173087169717071321189813039801561709179199299537261117051327109167213561163153923043099477297701919671517303839387849261589273833123079101159873477699057483247659819159243591249853539933571897321491957913401973873477143741853071859153423509111811:

Starting with 7

9367019841597357623467119171659917117897531437021419347913193363801053937411143551013783847501627627713467737623461921373011653063933061587449823653851289151143007567247103409813157831913667233729033933757837879147441329513409129843519239243219613811109409003303601319213009401923809109903209003007003009023099019083291049003129131063033009049011183169123429329153489219043159231447419787387573393309273327663191387513189043017427657003411519821583563289447851603393603561103731291643267377643177267261057483873101553411147393501083633913197439141207341357987117199561719117643267537951489107639: