Yes - all Lexington boards are masonite, including all the CS2.7s. I speculate that the masonite board contributes to the reported sonic advantages of the 2.7. There is a bit of mystery regarding how the 2.7 can sound so good with that huge 400uF electrolytic cap (albeit bypassed) in the midrange series feed.
Beetle - good memory. Those 1uF bypasses had been styrene / tin foil. Some sleuthing would be required to find out if, when and why they became PP - and on which models.