From what @tremblap said at the last FluCoMaChaT, fluild.bufnmfcross~ has changed a bunch already from what we “accidentally” got in alpha03, so this may already be the case, but it would be great to be able to specify @startframe & @numframes (ideally for both @source and @target).
Granted, one could fluid.bufcompose~ what they want first, but most(all?) of the other buf-based fluid.objects~ have some kind of specificity with regards to the desired frames to analyze.