I'm replying to finally report a successful double layer burning
What I did: edited in Premiere Pro 1.5, created menu in Encore 1.5 (build 188.8.131.52656 if matters). Imported DV files from Premiere and let Encore do automatic transcode. Built DVD Image to hdd.
First step of building the DVD image is transcoding. If you have done several tries, transcoding keeps availiable for the next buildings. Just re-does the menus, but not recompresses files.
After transcoding, when building, it asks where to place the layer break and offers a range of minutes (from xxxx to xxxx) from a certain file. The bigger the amount of free mbytes availiable on the disc the bigger range of minutes it will offer you. In my project automatic transcoding fitted quite well and just allowed me to choose in a 4 minutes range, because there was just 260mb of free space. Note this range of minutes doesn't mean total minutes of running the DVD, including the ones placed before, but minutes of running THAT file. So you can play that file separately on any player and see what minute and second fits better so the layer break is less noticeable.
Then I burnt the .IMG file with DVD Decrypter 184.108.40.206 IsoMode/Write with Bitsetting to DVD-ROM and using verbatim DVD+R DL 2.4x certified media. Burnt at 2.4x (took 47minutes) despite DVD Decrypter say it would support 4x too.
Here is the media info
Unique Disc Identifier : [DVD+R-DL:MKM-001-000]
Disc & Book Type : [DVD+R DL] - [DVD-ROM]
Manufacturer Name : [Mitsubishi Kagaku Media]
Manufacturer ID : [MKM]
Media Type ID : 
Product Revision : [Not Specified]
Blank Disc Capacity : [4,173,824 Sectors = 8,152.0MB = 7.96GB (8.55GB)]
Recording Speeds : [1x , 2.4x]
This disc plays great and the layer break takes very little, say 1/2sec, on my Dalton DVX500 settop player (Ascomtec). I'll test on other players as soon as I can, but I would bet it'll play on almost every player.
Hope this helps.