Agents said both had used a hotel room in Florida to drop off about 100 pounds of marijuana for a resident, who turned out to be cooperating with DEA agents.
The two were arrested in March in St. George. Vowell agreed in May to plead guilty to one of two charges and Sunyich to both charges filed against him.
In a memo to the court, Vowell's attorney wrote that he was on numerous medications for various medical conditions that may have impaired his decision-making and he also was being treated for anxiety and depression.
The presentence report characterized Sunyich as leader of a marijuana distribution scheme. But his attorney said in court papers that Sunyich began to sell marijuana to others after unsuccessfully trying to market medical marijuana in California where it is legal.
In asking for a reduced sentence, Sunyich cited his degree from Brigham Young University and his Mormon mission to New Zealand as examples of his character and fitness to live in society without committing further offenses.
The Piper Aerostar plane used to fly the marijuana was forfeited by Vowell, a friend, neighbor and business associate of Jeremy Johnson, another St. George businessman facing a federal lawsuit and criminal charges in a separate case involving his online mass sales company called I Works.
The plane was allegedly paid for by Johnson before being transferred to the ownership of a company controlled by Vowell, according to court-appointed receiver who took over Johnson's companies after he was sued by the Federal Trade Commission in 2010 for allegedly defrauding consumers.
Sunyich, his father, Steve, and siblings earlier this year also were sued by the FTC for an alleged scheme in which they bought consumers' information including credit card numbers from payday-loan companies and then began charging monthly fees without authorization.