Earths can't replace waters since shrink has a 100% success rate on beetles whereas terra sometimes misses. It's best if you just make alts and buy two weights, if you're making a wind knight make sure one of the weights is a -600 so that they can combo with their SPD pet, when the pet becomes faster just add SPD gears.

Make sure your Earth has over 4000 HP, even if it's a sealer. You can have 260 CON (or more) and 300 INT, but on higher end quest sealing is hard, so if you make just for high end go with all CON and some WIS so you can survive and spam stone wall and FS.