Man, this is the single worst part of the BJCP classifications, since Foreign Export and Tropical are both lumped into "Foreign Export Stout". Tropical Stouts are basically sweet stouts with a little more gravity. Probably not necessary to add unfermentables like lactose since you will be bumping the gravity up a bit from a typical sweet stout.
Here is what Jamil suggests in Brewing Classic Styles:
boil 60 min
14 lbs British Pale malt (or 10 lbs pale LME if extract)
3/4 lb roasted barley
10oz crystal 40
10oz crystal 80
1/2 lb chocolate malt
2.5 oz EKG 5%AA @60 min
WLP 013 or Wyeast 1028 (using an English yeast is important because of the slightly lower attenuation. For an export version, sub an American ale yeast like 1056. )
Ferment around 67F, raising to 70 at the end of fermentation for a diacetyl rest.