Here's how Milligan described the site to A&IGO Cooper in report of 1 Jul 1862: "One post at Drewry's Bluff, communicating [line of sight] with Chaffin's Bluff [across the James], thence down the river to Gregory's farm, where there is a good view for 15 miles. I found it impossible to get communication lower in consequence of the sinuous character of the river." (He apparently extended the line on south later on, perhaps aided by the artificial height of the "tower" or pigpen structure as shown on the map.)

We have a good description of the wartime Union signal service in Brown's "Sig Corps USA in the War of the Rebellion" and Miller's "Photographic History," among other sources (ref the website of the "Sig Corps Assn, 1860-1865" cited below, and especially its Forum, on which reenactors are prominent). The field kit comprised staffs of four 4-ft wooden sections (ash preferred), with one section bearing brass fitting to accommodate brass tube (thimb screws) for torch needed as the "flying" (swinging) torch for night signaling, which also used a second torch ("foot light") at feet of the sig man as ref point for distant viewer, both torches burning turpentine. The fitting for the flying torch was also a shield to keep flame from touching the wooden pole. The four sections were joined by friction-fit brass ferrules in tapering, telescoping fashion as mentioned earlier in these exchanges. (Not sure of tapering in originals -- photos appear to be same diameter sections.) The staff sections and other components of the kit (wicking, plyers, scissors, etc.) fitted in a cloth and "rubberized" cloth carrier with shoulder strap to be carried by one man. I've been unable to locate a first generation original for examination or image. Same considerations would have applied to CS (who certainly captured examples of Union sig equipment), but I have no info on their approach to sectionalized staffs, as opposed to single poles, which would have been awkward to carry, as you note. (Nor am I aware of other reasons for sectionalized poles, but would certainly think similar reasoning might have been applied to regular flag staffs, again as you state.)