You got me kinda stumped, I dont think it will work, both 15ampers would not split the load I believe you'd need two feeds (two separate plug runs) to do it that way even hooked in parallel regardless of load, they should both still blow at 15 amps; the second either fuse hits 15 amps they should both blow.
I'd just go get a 30 amp GFCI breaker (has a test button on the breaker), worth the cash (in case you ever pour water on your electricals) and would do the job as far as load