trying to work around disappearing sentences at the bottom of pages, by moving from mm to px, but without success unfortunately

command-line/css/print.css

@@ -93,13 +93,13 @@ body{
     /*size: 152.4mm 228.6mm;*/ /* Size of the online PDF */
     /*size: 152mm 229mm;*/ /* Size listed in cover generator of Lightning Source */
     /*size: 164mm 237mm;*/ /* Size of the physical printed DB06 book */
-    size: 152.4mm 228.6mm;
+    size: 576px 864px;
+    /*size: 152.4mm 228.6mm;*/
 
-    /* about 3mm in pixels */
+    /* 3mm =~ 12px */
     bleed: 12px; 
     marks: crop;
 
-
     @bottom-center{
         content: counter(page);
         font-size: 9.5pt;
@@ -107,10 +107,12 @@ body{
     }
 }
 @page:right{
-    margin: 14.758mm 18mm 21.225mm 29.125mm;
+    margin: 55px 18mm 80px 29.125mm;
+    /*margin: 14.758mm 18mm 21.225mm 29.125mm;*/
 }
 @page:left{
-    margin: 14.758mm 29.125mm 21.225mm 18mm;
+    margin: 55px 29.125mm 80px 18mm;
+    /*margin: 14.758mm 29.125mm 21.225mm 18mm;*/
 }
 @page:right{
     /* running header: contribution title (taken from the h2 of the contribution) */