Actually, believe it or not, although skiddo are typically smaller than seel, you should have no problem placing your seel on your skiddo’s back and have it ride without any further cushioning or restraints. Skiddo can take a surprising amount of weight; some have even been known to carry new trainers for hours at a time. So I wouldn’t worry so long as your skiddo is comfortable carrying seel and so long as your seel is comfortable riding on its friend’s back.
Unless, of course, you’re actually referring to multiple seel, as the “them” might also imply, at which point you may wish to consider strapping baskets to your skiddo’s back.