The cupola module looks great and I want to put them everywhere on stations, but seems a bit heavy compared to other similar modules. Its mass at 4.54 makes it the highest of the command modules (the mk1-2 is only 4.12). It's less functional than similar pieces, the lander can weighs substantially less, but fits more kerbals and has stronger gyros. Glass is admittedly heavy, but it still seems like it's a bit overweight for an essentially cosmetic part.