Double towing, any 2 trailers [or Triple Towing, if you will] is legal in Wyoming. There are weight limits & stopping requirements
for towing a 2nd trailer without brakes. Also check your Dr Lic requirements, depending on total GVWR. Good info on the links below.
If you plan to tow outside of WY, (as others have said) be aware of their various restrictions/laws, including that some require
the first trailer to be a 5th wheel. See #43 below, from this site:
http://www.towingworld.com/articles/TowingLaws.htm
Footnote # 43. With certain qualifications. Only with fifth-wheel trailer in Arizona, Illinois, Michigan, Minnesota,
Manitoba (maximum length 23m.) and Saskatchewan.
http://www.brakebuddy.com/Towing-Laws
http://www.readybrake.com/state_laws.html
Legalities aside -- here's some food for thought in reference to your questions.
Logically, there's going to be greater potential for (rear) trailer sway... especially with passing traffic or cross-winds.
Will the weight of the 2nd trailer affect (lessen) the tongue weight of your TT??... which could also affect towing.
Will the weight of 2nd trailer put you at (or over) the Springdale's GVWR and/or the axle ratings??
Hopefully other members with your same trailer can offer more info.
Terri, the Chevy co-pilot & DH Kevin