People who advocate bridging by taking a short acting oral in the morning are ignoring a couple of important points. First, low doses of dbol have been shown in a number of studies to suppress test production. Bridging advocates say that yes, that may be true, but you can avoid that by taking your dbol in the morning after your test has had its morning peak.
The problem with that reasoning is that while test shows a definite diurnal rythym (highest in AM), LH shows much less variation through the day and night. GnRH, which is secreted by the hypothalamus and is responsible for LH secretion and ultimately test output, cannot be measured in the blood. However, mathematical models of the HPA that correspond to observations show GnRH output as consisting of a regular series of bursts throughout the day and night with no diurnal variation.
Dbol and all other androgens act on the hypothalamus to alter GnRH output. So if there is no morning peak in GnRH, as models predict, then the dbol is going to screw up GnRH production no matter when you take it.